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Abstract
Optical parametric chirped-pulse-amplification produces two broadband pulses, a signal and an idler, that can both provide peak powers >100 GW. In most cases the signal is used, but compressing the longer-wavelength idler opens up opportunities for experiments where the driving laser wavelength is a key parameter. This paper will describe several subsystems that were added to a petawatt class, Multi-Terawatt optical parametric amplifier line (MTW-OPAL) at the Laboratory for Laser Energetics to address two long-standing issues introduced by the use of the idler, angular dispersion, and spectral phase reversal. To the best of our knowledge, this is the first time that compensation of angular dispersion and phase reversal has been achieved in a single system and results in a 100 GW, 120-fs duration, pulse at 1170 nm.
© 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
1. Introduction
Sources of energetic, ultrafast pluses in the mid- and near-infrared are required for a number of applications, — for example, high harmonic generation (HHG) and Raman plasma amplifiers (RPA’s). In the case of HHG, where attosecond pulses in the extreme ultraviolet (XUV) are produced, a higher bandwidth XUV pulse is possible when longer-wavelength drivers are used [1,2]. Similarly an RPA promises to overcome the damage limitations of chirped-pulse-ampflication (CPA) compression gratings by using a “damage-free” plasma to transfer energy from a multipicosecond high-energy pulse to a longer-wavelength femtosecond seed pulse [3]. This technology promises to achieve focused intensities exceeding $10^{23}\mbox { W/cm}^2$ if pumped with a the output of an Nd:glass-based CPA system laser [4] but requires a 1100-nm to 1250-nm seed pulse. Simulations show that seed parameters, a high-intensity ($10^{15}\mbox {W/cm}^2$) with a sub-200-fs pulse duration, enable efficient amplification in a regime with minimal plasma instabilities [5,6]. In both RPA and HHG, high-peak powers allow for high intensities over large focal volumes, where better phase matching and energy transfer can occur. In summary, sources that produce long-wavelength, high-energy, femtosecond pulses are a key component for pushing the boundaries of these exotic generation schemes.
Optical-parametric-chirped-pulse-amplification (OPCPA) systems [7] have historically been attractive due to their high peak and average powers [8]. They have the additional advantage of producing two broadband pulses: a signal, which is seeded, and an idler, which has a wavelength set by the difference frequency generation process. Using the idler requires overcoming two disadvantages that are a result of phase matching and energy conservation. First, phase matching in a noncollinear optical parametric amplifier (NOPA) [9] produces an idler that is angularly dispersed, which hampers pulse focusing and compression. Second, energy conservation impedes pulse compression by inverting the spectral phase of the idler relative to the signal [10]. This phase change reverses the sign of group-delay dispersion (GDD), fourth-order dispersion (FOD), and higher even orders, while maintaining the sign of all odd orders, such as third-order dispersion (TOD) [11,12]. As a result, the spectral phase requirements for an idler compressor and signal stretcher are vastly different from standard CPA schemes. Ideally, the idler compressor and signal stretcher will have the GDD and FOD that are approximately equal in magnitude and sign, while the TOD is approximately equal in magnitude and opposite in sign. For transform-limited compression, other minor sources of dispersion (material, coating, etc.) must also be taken into account. While the majority of OPCPA systems use the signal and neglect the idler, several systems have been built and designed around using the idler to produce power and wavelength combinations that are otherwise difficult to achieve [13–25].
Employing the idler from a terawatt or petawatt OPCPA system further exacerbates the challenges introduced by the idler. The majority of idler OPCPA systems built so far have mitigated angular dispersion by using collinear, or quasi-collinear geometry [13–24]. In order to maintain bandwidth with a collinear geometry, many of these systems use quasi-phase-matched nonlinear crystals, such as periodically poled lithium niobate, which have lower damage thresholds and smaller apertures compared to crystals that can be critically phase matched, such as deuterated potassium dihydrogen phosphate (DKDP), lithium triborate (LBO), or potassium titanyle arsenate. With these quasi-phase-matched nonlinear crystals, the idler energy produced is severely limited. Similarly, many idler OPCPA systems also depend heavily upon higher-order dispersion compensation from devices like the acoustic-optic programmable dispersive filter (AOPDF) and other adaptive phase controls to overcome the idler-to-signal phase inversion [13–20]. However, using an AOPDF to reverse the TOD is effective only when stretched-pulse durations are relatively short ($<10\mbox { ps}$). While AOPDFs have been used extensively in many idler OPCPA systems [14,16–18,20], their ability to reverse TOD does not scale to systems with terawatt or petawatt peak powers which can require a stretched pulse duration of up to a $~10\mbox { ns}$ [26–33]. In summary, modifying a petawatt OPCPA system for maximum idler intensity requires both angular dispersion compensation and addressing phase reversal through stretcher/compressor design.
Here, we describe techniques to optimize the peak intensity of the idler by addressing both the phase reversal and angular dispersion of an existing petawatt OPCPA system. The system is MTW-OPAL [34,35], a 0.35-PW optical parametric amplifier line that is pumped by the Multi-Terawatt (MTW) laser at the Laboratory for Laser Energetics [36]. With the addition of several optical subsystems, MTW-OPAL is able to function in an alternative idler mode, which we will refer to as idler OPAL. To the best of our knowledge, this is the first time compensation of both angular dispersion and phase reversal has been achieved in a single system and capable of producing 100-GW pulses at 1170 nm with 120-fs durations.
2. Experiment
In its normal operation MTW-OPAL consists of an ultrabroadband front end (UFE), a cylindrical Öffner stretcher (COS), a power amplifier (N4), and a final DKDP amplifier (N5) as shown in Fig. 1(b). The purpose of MTW-OPAL is to demonstrate broadband amplification in DKDP crystals with a frequency-doubled Nd:glass pump laser, where the gain is centered at a wavelength of 910 nm and petawatt pulses are produced [34,35]. While DKDP is used in N5 to amplify a 45mm-square beam, the earlier NOPA stages – N2, N3, N4a, and N4b – use smaller beam sizes and use beta-barium borate (BBO) due to its higher nonlinear coefficient [37]. For ease of switching between the conventional MTW-OPAL configuration [Fig. 1(b)], which produces 7-J, 20-fs pulses at 910 nm, and an idler OPAL configuration [Fig. 1(a)], which produces 20-mJ, 120-fs pulses at 1170 nm, many of the subsystems were left unchanged between the two modes of operation. The differences between the conventional and idler OPAL operation include using an alternate grism stretcher (GrS) for the signal, operating at a reduced bandwidth, and bypassing the final amplifier (N5). Two additional subsystems, an angular dispersion compensator (ADC) and an idler-specific grating compressor (IGC), were built to collimate and compress the idler.
Fig. 1. (a) A schematic of the idler OPAL and (b) standard MTW-OPAL configurations shows that they share many components including the ultrabroadband front end (UFE), the pre-and power amplifiers (N4a and N4b), and a nanosecond-pump laser. (a) Systems added to operate idler OPAL include an alternate grism stretcher (GrS), angular dispersion compensation (ADC), and an idler specific grating compressor (IGC). (b) The components of MTW-OPAL that are unused are the final amplifier which is pumped by the MTW laser (N5), a cylindrical Öffner stretcher (COS), and grating compressor chamber (GCC).
No changes were made to the UFE, which consists of a home-built fiber chirped-pulse amplifier (FCPA), a picosecond pump laser, a system for generating white-light continuum (WLC), an AOPDF, and three NOPA’s (N1 to N3). White light continuum from 650 nm to 1100 nm is generated from focusing a portion of the output of an FCPA (500 kHz, 14 $\mathrm {\mu }$J, 300 fs, 1050nm) onto a YAG plate. This serves as the seed for the N1, which is pumped by the frequency-doubled remaining portion of the fiber CPA laser. The first three NOPA stages, N1 to N3, have an internal noncollinear angle between the pump and signal of $2.23^{\circ }$. Prior to N2 and N3 the pulse is stretched using an AOPDF (Dazzler, Fastlite [38]) to 6 ps. N2 and N3 are pumped with a 5-Hz Nd:YLF laser (EKSPLA), which is seeded by the FCPA laser. These 11-ps pump pulses are amplified to 70 mJ, frequency doubled with a lithium triborate (LBO) crystal, and split into two arms, each of which is imaged onto the N2 and N3 crystals. The N3 pulse exiting UFE has a 7-mm-diameter super-Gaussian-beam profile, 3.5 mJ of energy, and 200 nm bandwidth centered at 910 nm.
Due to the phase reversal of the idler, an alternate GrS was designed and built between N3 and N4 [12] to replace the COS. In order to use a conventional Treacy compressor (which has negative GDD and positive TOD) to compress the idler, a seed stretcher with both negative GDD and negative TOD was designed and built. This was accomplished with a pair of grisms manufactured from $45^{\circ }$ apex, uncoated, SF57 prisms mounted 1 mm away from gold-coated 1480 LP/mm gratings, optimized for p-polarized pulses. After the second grism, a roof mirror sends the pulse back through the grism pair to remove the spatial chirp and double the stretched pulse duration to 1 ns. This design is able to fully compensate GDD and TOD over 40 nm of bandwidth. Residual FOD is only partially compensated because of limitations in the available prism sizes [12]. Another consequence of the limits in prism size is that the stretched signal pulse duration (1 ns) is only two-thirds of the N4 pump pulse duration that was optimized for MTW-OPAL (1.5 ns). In addition, to maintain high spectral intensity at the wavelengths ideal for Raman amplification experiments rather than produce the shortest possible pulse durations, the GrS design was optimized to support only 40-nm of signal bandwidth.
The optical path length of the GrS was significantly shorter than the COS so an alternate image relay was required to image the N3 signal on to the N4a crystal while maintaining the same signal beam sizes with a magnification of $0.6\times$. Transport between N4a to N4b used the same $2.3\times$ vacuum spatial filter (VSF) that is used in normal MTW-OPAL operation.
Operation of the nanosecond-pump laser, which is used to pump N4a and N4b, also remained unchanged. This pump laser is based on a Nd:YLF laser [39] and is electronically synchronized with the FCPA laser in the UFE. It is frequency-doubled in LBO to 527 nm and split into two arms, each are imaged onto the N4a and N4b crystals; the N4a pump has 70 mJ in a 3-mm square beam while the N4b pump has 450 mJ in a 7-mm square beam. The delay of the pump laser was changed to account for the shorter propagation time through the GrS compared to the COS.
The N4a and N4b amplifiers are able to reach similar energy levels of output (15 mJ and 125 mJ) with the GrS as in the conventional MTW-OPAL operation, despite the reduced temporal overlap of the pump to the seed because of high throughput of the GrS. The N4a and N4b have the same noncollinear angle as the three NOPA stages used in UFE ($2.23^{\circ }$), but due to the larger beam sizes, dichroic mirrors are used to combine and remove the pump. In N4a the slightly smaller square aperture of the pump apodizes the amplified signal. The idler exits the N4b crystal at $\sim 8.5^{\circ }$ with respect to the signal. The dichroic mirror separates the pump from the signal and idler and the idler is spatially separated from the signal with a D-cut mirror. The idler has 85 mJ of energy and a bandwidth of 45 nm centered at 1170 nm with the angular dispersion predicted to be $123\mbox { }\mu \mbox {rad/nm}$ based on phase matching calculations in BBO.
Idler angular dispersion is compensated by imaging the N4b nonlinear crystal onto the input face of the first of two custom prisms. The first prism (P1 in Fig. 3) is manufactured from N-KZFS2 (Schott) and has an apex angle of $74^{\circ }$, and second prism (P2 in Fig. 3) is made from S-TIH53 (Ohara) and has an apex angle of $22^{\circ }$. These prisms are antireflection coated and oriented so the apices are pointed in opposing directions, and each is set to have an incidence angle of least deviation. Together the two prisms produce a linear angular dispersion of 40.9 $\mu$rad/nm and quadratic angular dispersion of $-0.006\mbox { }\mu \mbox {rad/nm}^2$ without introducing noticeable ellipticity into the beam. The importance of the second prism is to remove quadratic angular dispersion without significantly reducing the linear angular dispersion introduced by the first prism. A $3\times$ imaging system matched the linear angular dispersion of the prism pair to the idler and is made up of two custom achromats (400 mm, 1200 mm). Several lens options were considered for this imaging system, including singlets and spherical reflectors, but both had disadvantages compared to the custom achromats. Space constraints near the N4b crystal made spherical reflectors unattractive to align while a ray-tracing analysis of a design based on singlets showed the introduction of significant spatialtemporal coupling when imaging an angularly dispersed beam. It is suspected that the dominant source of spatialtemporal coupling is from spherical and coma aberrations [40]; therefore, achromats designed with zero spherical and coma aberrations over the idler wavelength range [41] minimize these effects. As built, the ADC was able to reduce angular dispersion perpendicular to polarization from $123\mbox { }\mu \mbox {rad/nm}$ [Fig. 2(a)] to $<0.5\mbox { }\mu \mbox {rad/nm}$ [Fig. 2(b)].
Fig. 2. (a) The idler far field before the two prisms is primarily elongated by a factor of $\sim 20\times$ due to angular dispersion, which is primarily in the direction of the noncollinear angle between pump and signal. (b) The far field after the two prisms (measured with the same lens) has a horizontal angular dispersion, reduced to $0.5\mbox { }\mu \mbox {rad/nm}$. Residual vertical angular dispersion, which is of the order of $2 \mbox { }\mu \mbox {rad/nm}$, is not compensated by the prisms, but by a small mismatch in grating tilt in the compressor.
Fig. 3. The idler has angular dispersion both perpendicular and parallel to its polarization. The majority of angular dispersion is perpendicular to polarization and a result of the noncollinear angle between the pump and signal (not shown to simplify the schematic). Angular disperison parallel to polarization is due to misalignment of the pump and signal away from the horizontal plane or misalignment of the compressor grating tilt. Polarization is rotated between the ADC and IGC with a periscope (P). Residual angular dispersion was measured with the focal-spot diagnostic (FSD), made up of an 800 mm focusing lens and a charge coupled device (CCD), and compensated in each direction through a small change in the rotation of P2 in the ADC and G2 in the IGC.
After the majority of angular dispersion is compensated, the collimated idler is further magnified with a pair of achromats (preventing the introduction of radial-group-delay [42]) to a beam size of 33 mm, to prepare it for the grating compressor. The compressor is comprised of two parallel 1285 LP/mm gratings (PGL) with a roof mirror used to double pass the system. Slant distance and grating input angle are selected to maximize peak power at the output of the compressor as measured with a custom IR-SPIDER (APE Angewandte Physik and Elektronik GmbH [43]). The compressed pulse was measured to have a full-width-half-maximum (FWHM) pulse duration of $120\pm 10$ fs with a spectrum to support a transform limited pulse FWHM duration of 50 fs [Fig. 4(b)]. Pulse duration was sampled in multiple locations across the near field to ensure that there was no measurable spatially dependent chirp.
Fig. 4. (a) The idler phase is measured over 100 shots by the IR-SPIDER, and is denoted by the shaded area. The average phase and spectrum are shown by the solid grey line and dotted line, respectively. This phase closely matches the expected phase (blue line) where the residual fourth-order dispersion (FOD) is balanced by a nonzero group delay dispersion (GDD). (b) The measured peak power is $4\times$ lower than transform limited (black dotted line), but matches the temporal pulse predicted by the design of the grism stretcher/grating compressor pair.
The idler focal spot was measured after the compressor with a focal-spot diagnostic (FSD), made up of an 800-mm lens (a copy of the experimental focusing lens) and with two types of cameras at the focal plane — a silicon chip camera (Manta 145B-NIR), which has a 6.45-$\mu$m pixel pitch but poor spectral sensitivity, and an InGaAs chip camera (Xenics Bobcat 640), which has a 20-$\mu$m pixel pitch and good spectral sensitivity. This diagnostic was also used to measure residual angular dispersion by blocking all but two wavelengths in the GrS by placing a mask in front of the roof mirror. Measuring the centroid the focii of each of these wavelengths on the InGaAs camera allowed for a quick angular dispersion measurement even when angular dispersion was hidden by monochromatic aberrations that enlarged the focii. A study of angular dispersion versus spot size showed that both cameras measured identical spot sizes when magnitude of the angular dispersion was less than $2\mbox { }\mu \mbox {rad/nm}$.
3. Results and discussion
The focused and compressed idler maintained a day-to-day peak intensity of $5\times 10^{15}$ W/cm$^2$, which is about an order of magnitude lower than the diffraction-limited and transform-limited intensity. The diffraction- and transform-limited intensity is based on the measured near-field beam profile and spectrum (row 1 in Table 1). Reduction of this peak intensity is calculated from a subset of spatiotemporal effects: linear angular dispersion, residual spectral phase, and monochromatic wavefront. How each of these spatiotemporal effects would individually impact the achievable peak intensity is calculated in rows 2-4 in Table 1, according to the formalism described in Appendix A. In the fifth row of Table 1, all three spatiotemporal effects are applied. A detailed explanation of each of these spatiotemporal effects as well as energy throughput, is discussed in the remainder of this section. Also discussed are the drawbacks of simplifying the design by compensating angular dispersion with a tilt of the grating compressor and additional concerns of scaling this work to full MTW-OPAL spectrum and energy.
Table 1. Contributions to peak intensity.
Pulse energy is primarily a function of the idler optics, which have a net throughput of approximately $20\%$. It was not possible to increase N4a and N4b signal and idler energy, since both amplfiers were operated near their damage threshold. However, only half of the idler energy loss was due to dispersive elements; the prisms in the ADC had a throughput of $68.3\%$ and the compressor gratings and roof mirror had a throughput of $82.1\%$. The remaining loss came from the large number of mirrors ($>10$) needed to guide the beam around the existing OPAL components.
The design of the stretcher and compressor maintained low GDD and TOD, but had a significant residual FOD ($1\times 10^7 \mbox { fs}^4$), which caused the largest reduction in peak intensity. Using a grism rather than grating stretcher allowed for a pulse with zero TOD, and without such a stretcher large amount of residual TOD would remain (green line in Fig. 5) which would have resulted in a peak intensity that would have been further reduced by a factor of 4. The stretcher design that was built (blue line in Fig. 5) was a result of a compromise between further reducing residual FOD and grism sizes that were prohibitively large [12]. Reducing the residual FOD of the compressed pulse could be achieved in additional two ways: (1) tilting the gratings relative to the prisms in the grism stretcher, or (2) programming an alternate phase into the AOPDF. Previous work on grism stretchers for other applications show promising results from tilting the gratings relative to the prisms [44–46], an avenue that was not explored in this work. Changes to the AOPDF were also neglected in here in order to simplify the changeover between the two modes of operation. The AOPDF does have the capability to further reduce residual FOD but adds complexity because the AOPDF used in MTW-OPAL also serves as a stretcher for the N2 and N3 amplifiers. As a result there exist limitations on spectral phase orders which are to maintain temporal overlap with the N2 and N3 pump pulses. These limitations are reduced by only stretching a 40-nm subset of the entire MTW-OPAL bandwidth with the AOPDF, changes to the GDD can balance out the additional FOD needed to make an impact on the final compressed pulse. Modeling shows that adding GDD = $4\times 10^4\mbox { fs}^2$, TOD = $3\times 10^5\mbox { fs}^3$, and FOD = $1\times 10^7\mbox { fs}^4$ with the AOPDF would reduce the FWHM pulse duration from 120 fs to 72 fs (red line in Fig. 5).
Fig. 5. (a) The compressed phase of the original grism stretcher design (blue line), expected phase if stretched with a grating pair stretcher (green dotted-dashed line), and original grism stretcher with additional phase programmed into the AOPDF (dashed red line) along with a predicted spectral intensity (dotted black line). (b) The peak power of each of these options is reduced from transform limited (dotted black line).
Monochromatic aberrations from the idler wavefront reduced the peak intensity by more than a factor of 2. It is well known that the idler wavefront is inherited from the pump wavefront [47] and here the majority of the idler wavefront error was a result of that relationship. This can be seen in the similarities in the focal spots of pump and idler; both had far fields with shot-to-shot spot size with a standard deviation of $30\%$. Because the N4 pump laser was initially designed for signal amplification, pump induced wavefront degradation had not been considered. Due to shot-to-shot variation in wavefront, standard methods of correcting wavefront, such as a phase corrector or deformable mirror, could not be used. This variation in wavefront motivated the focal spot diagnostic (FSD, Fig. 3). This diagnostic measured an average peak fluence that was an order of magnitude lower that the diffraction limited and a spot radii that ranged from $1.1\times$ to $4\times$ over the diffraction limit.
Finally, angular dispersion had the least impact on peak intensity. At the exit of the compressor, the magnitude of linear angular dispersion was kept below 0.5 $\mu$rad/nm in both directions — the resolution of the angular dispersion diagnostic described above. Angular dispersion contributes to the spectral phase through a spatiotemporal coupling term (Appendix A) and decreases peak intensity by $12\%$. Angular dispersion had no discernible reduction in fluence when the residual angular dispersion had a magnitude less than 1 $\mu$rad/nm (as measured by the focal spot diagnostic, Fig. 3). Residual linear angular dispersion of less than 0.5 $\mu$rad/nm was maintained by rotating dispersive optics in the idler path that were either parallel or perpendicular to polarization. In-plane tilt of the second ADC prism (P2 in Fig. 3) could compensate angular dispersion perpendicular to polarization, while in-plane tilt of the second compressor grating (G2 in Fig. 3) could compensate angular dispersion parallel to polarization. The angular dispersion per degree of optic rotation was mapped for both G2 and P2. The maximum rotation of P2 was limited to preserve a near-field beam ellipticity of $10\%$($\pm 5^{\circ }$); the maximum rotation of G2 ($\pm.02^{\circ }$) was limited so that changes to compressor GDD could be easily compensated by slant distance. Because of these limitations, the N4b idler angular dispersion must match the predicted angular dispersion within 2 $\mu \mbox {rad/nm}$. To achieve this, the N4b pump-signal angle was set to $2.23^\circ$ by measuring the focii of the input N4b pump and signal with an 100-mm achromat prior to aligning the remainder of the system.
The effect of the predicted residual quadratic angular dispersion on the peak intensity was studied and found to be negligible. A quadratic angular dispersion term of $-0.006\mbox { }\mu \mbox {rad/nm}^2$ was added to the spectral phase term used to calculate intensity (as described in Appendix A). The main contribution to quadradic angular dispersion is from the prisms in the ADC, and the values of quadradic AD used in calculations were based on prism specifications. During the design, the second prism was added to remove quadratic angular dispersion introduced by the first prism, which would have otherwise been $0.024\mbox { }\mu \mbox {rad/nm}^2$. Calculations showed that while this second prism led to a large improvement to the transform- and diffraction-limited pulse, but its effect was negligible for a pulse with large residual FOD and non-diffraction limited spot quality. Despite this, we continue to operate the ADC with both prisms.
As described, above tilting the compressor gratings is an effective tool to tune out residual angular dispersion and could have been used to fully compensate N4b idler angular dispersion without a separate ADC. Calculations show that a $5^{\circ }$ tilt angle would be able to match the angular dispersion of the up-collimated idler, however such a scheme has several drawbacks. First, because of the polarization of the idler is perpendicular to the direction of angular dispersion, the compressor gratings would need to be oriented in a transverse-electric mode, which typically has lower throughput for gold gratings. Second, there would be less flexibility to control higher order angular dispersion. Without a separate ADC, additional dispersive optics could not be introduced, such as P2, to control higher orders of angular dispersion, putting more pressure on the compressor design. Finally, imaging the angularly dispersed idler to the compressor beam diameter would require careful modeling to prevent spatiotemporal coupling impairments (such as those that motivated use of achromats in the ADC), which scales with increased beam diameter [40].
The above methodology can be also be applied to the idler that is produced by the final MTW-OPAL amplifier, N5 [Fig. 1]. The N5 idler exits the DKDP crystal with 12 J and has 400 nm of bandwidth centered at 1250 nm and if angular disperison and the spectral phase reverseal was addressed could lead to a 300 TW pulse at 1250 nm. In order to take advantage of the entire OPAL spectrum, a redesign of the stretcher would be required. Such a stretcher would still be grism based, but need less dispersion per nanometer as well as full compensation of FOD (and higher orders). Compensating the N5 idler angular dispersion would require dispersive optics for a 45-mm beam size. Unfortunately, magnification at these sizes would be of limited use in matching linear angular dispersion between N5 and dispersive optics because both optic manufacturing and fluence levels are near their limits. In addition, higher orders of angular dispersion would need to be considered due to the larger beam sizes. Also, due to large beam sizes, separating the idler from the signal would likely require spectral filters rather than spatial separation and would potentially limit the peak power through coating damage or throughput. One advantage of using the idler from N5 is improved wavefront, which has been carefully controlled in the MTW laser, therefore an improved idler focal-spot quality would be expected.
In conclusion, the compression of the idler to 100 GW peak powers from an existing OPCPA system has been demonstrated. An alternate stretcher and angular dispersion compensation allowed the use of a standard grating compressor. The design of both the stretcher and angular dispersion compensation scheme required modeling of both higher-order spectral phase and angular dispersion. Minimizing switchover time between the conventional signal MTW-OPAL mode and the idler OPAL mode was achieved by changing as few as possible of the existing MTW-OPAL components. While this system produces 100 GW pulses, the techniques described here are appropriate to scale this work to terawatt and petawatt levels provided higher-order spatiotemporal coupling and optic availability was addressed. Utilizing the idler from high-peak-power OPCPA systems offers increased wavelength flexibility and provides a unique opportunity to further study the limits of laser technology.
Appendix A: Calculation of peak intensity
Here, we show how the pulse intensity is estimated based on the measured values of spectral intensity, $S(\lambda )$, near-field profile, $F_{\textrm {NF}}(x,y)$, angular dispersion, $\frac {\textrm {d}\theta }{\textrm {d}\lambda }$, far-field profile, $f(u,v)$, and IR-SPIDER measured phase ($\phi _S)$. Different values of $\frac {\textrm {d}\theta }{\textrm {d}\lambda }$, $f(u,v)$, and $\phi _S$ are used to calculate the pulse intensity for the five different cases listed in Table 1. In the first row, the diffraction and transform limited intensity, $I_0$, is based solely on measured values of $S(\lambda )$, $F_{\textrm {NF}}(x,y)$. In rows 2 to 4, only one of $\frac {\textrm {d}\theta }{\textrm {d}\lambda }$, $f(u,v)$, or $\phi _S$ is set to its measured value. In the fifth row, all the measured values are used to calculate an accurate peak intensity at the experimental plane.
In all calculations, we make the lowest-order assumption that the time-dependent intensity in the far field, $I(t,u,v)$ has its maximum $I_0$ at the same time ($t_0$) and location ($u_0,v_0$),
as the peak power ($P_0$) and as the peak fluence ($F_0$) Therefore, we can make the following assumption which allows an estimation of the peak intensity without a wavelength-dependent wavefront measurement to capture spatiotemporal coupling. The peak fluence and peak power are used to connect the dimensionless, peak normalized functions for fluence, $f(u,v)$ and power, $p(t)$ to the pulse energy ($E_0$) using and The peak-normalized focal fluence, $f(u,v)$, is measured using the FSD camera where $(u,v)$ are far-field coordinates. The peak-normalized, time-dependent power, $p(t)$ is calculated from the near-field intensity, where $(x,y)$ are near-field coordinates. The near-field intensity is the temporal Fourier transform of the near-field spectral amplitude $S_{\textrm {NF}}(\lambda,x,y)$ and spectral phase $\phi _{\textrm {NF}}(\lambda,x,y)$,Funding
Department of Energy Office of Science (DE-SC0016253); National Nuclear Security Administration (DE-NA0003856).
Acknowledgments
This report was prepared as an account of work sponsored by an agency of the U.S. Government. Neither the U.S. Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the U.S. Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the U.S. Government or any agency thereof.
Disclosures
The authors declare no conflicts of interest.
Data availability
Data underlying the results presented in this paper are not publicly available at this time but may be obtained from the authors upon reasonable request.
References
1. P. M. Paul, E. S. Toma, P. Breger, G. Mullot, F. Augé, Ph. Balcou, H. G. Muller, and P. Agostini, “Observation of a train of attosecond pulses from high harmonic generation,” Science 292(5522), 1689–1692 (2001). [CrossRef]
2. T. Popmintchev, M.-C. Chen, P. Arpin, M. M. Murnane, and H. C. Kapteyn, “The attosecond nonlinear optics of bright coherent x-ray generation,” Nat. Photonics 4(12), 822–832 (2010). [CrossRef]
3. V. M. Malkin, G. Shvets, and N. J. Fisch, “Fast compression of laser beams to highly overcritical powers,” Phys. Rev. Lett. 82(22), 4448–4451 (1999). [CrossRef]
4. J. H. Kelly, L. J. Waxer, V. Bagnoud, et al., “OMEGA EP: High-energy petawatt capability for the OMEGA Laser Facility,” J. Phys. IV France 133, 75–80 (2006). [CrossRef]
5. J. D. Sadler, “Optimisation and applications of Raman plasma amplifiers,” Ph.D. thesis, University of Oxford (2017).
6. D. Haberberger, A. Davies, J. L. Shaw, R. K. Follett, J. P. Palastro, and D. H. Froula, “Hot Raman amplification,” Phys. Plasmas 28(6), 062311 (2021). [CrossRef]
7. A. Dubietis, G. Jonušauskas, and A. Piskarskas, “Powerful femtosecond pulse generation by chirped and stretched pulse parametric amplification in BBO crystal,” Opt. Commun. 88(4-6), 437–440 (1992). [CrossRef]
8. A. Vaupel, N. Bodnar, B. Webb, L. Shah, and M. C. Richardson, “Concepts, performance review, and prospects of table-top, few-cycle optical parametric chirped-pulse amplification,” Opt. Eng. 53(5), 051507 (2013). [CrossRef]
9. T. Wilhelm, J. Piel, and E. Riedle, “Sub-20-fs pulses tunable across the visible from a blue-pumped single-pass noncollinear parametric converter,” Opt. Lett. 22(19), 1494–1496 (1997). [CrossRef]
10. I. N. Ross, P. Matousek, G. H. C. New, and K. Osvay, “Analysis and optimization of optical parametric chirped pulse amplification,” J. Opt. Soc. Am. B 19(12), 2945–2956 (2002). [CrossRef]
11. I. V. Yakovlev, G. I. Freidman, E. V. Katin, E. A. Khazanov, A. V. Kirsanov, and M. A. Martyanov, “Stretcher-compressor design for OPCPA system with chirp reversal,” in Proceedings Volume 6614, Laser Optics 2006: Superintense Light Fields and Ultrafast Processes (SPIE, 2007).
12. S. Bucht, D. Haberberger, J. Bromage, and D. H. Froula, “Methodology for designing grism stretchers for idler-based optical parametric chirped-pulse-amplification systems,” J. Opt. Soc. Am. B 36(8), 2325–2337 (2019). [CrossRef]
13. Y. Akahane, O. Kanade, K. Tsuji, M. Aoyama, and K. Yamakawa, “Idler pulse compression with an identical positive dispersive media to signal pulse stretcher in ultrafast optical-parametric chirped pulse amplification,” Optical Technical Digest Series (CD) (Optical Society of America, 2010), paper ATuA8.
14. B. W. Mayer, C. R. Phillips, L. Gallmann, M. M. Fejer, and U. Keller, “Sub-four-cycle laser pulses directly from a high-repetition-rate optical parametric chirped-pulse amplifier at 3.4μm,” Opt. Lett. 38(21), 4265–4268 (2013). [CrossRef]
15. P. Rigaud, A. V. de Walle, M. Hanna, N. Forget, F. Guichard, Y. Zaouter, K. Guesmi, F. Druon, and P. Georges, “Supercontinuum-seeded few-cycle mid-infrared OPCPA system,” Opt. Express 24(23), 26494–26502 (2016). [CrossRef]
16. X. Zou, W. Li, H. Liang, K. Liu, S. Qu, Q. J. Wang, and Y. Zhang, “300 μJ, 3 W, few-cycle, 3 μm OPCPA based on periodically poled stoichiometric lithium tantalate crystals,” Opt. Lett. 44(11), 2791–2794 (2019). [CrossRef]
17. M. Bock, L. von Grafenstein, U. Griebner, and T. Elsaesser, “Generation of millijoule few-cycle pulses at 5μm by indirect spectral shaping of the idler in an optical parametric chirped pulse amplifier,” J. Opt. Soc. Am. B 35(12), C18–C24 (2018). [CrossRef]
18. N. Thiré, R. Maksimenka, B. Kiss, C. Ferchaud, G. Gitzinger, T. Pinoteau, H. Jousselin, S. Jarosch, P. Bizouard, V. D. Pietro, E. Cormier, K. Osvay, and N. Forget, “Highly stable, 15 W, few-cycle, 65 mrad CEP-noise mid-IR OPCPA for statistical physics,” Opt. Express 26(21), 26907–26915 (2018). [CrossRef]
19. P. Fuertjes, L. von Grafenstein, D. Ueberschaer, C. Mei, U. Griebner, and T. Elsaesser, “Compact OPCPA system seeded by a Cr:ZnS laser for generating tunable femtosecond pulses in the MWIR,” Opt. Lett. 46(7), 1704–1707 (2021). [CrossRef]
20. N. Bigler, J. Pupeikis, S. Hrisafov, L. Gallmann, C. R. Phillips, and U. Keller, “High-power opcpa generating 1.7 cycle pulses at 2.5 μm,” Opt. Express 26(20), 26750–26757 (2018). [CrossRef]
21. A. V. Mitrofanov, D. A. Sidorov-Biryukov, A. A. Voronin, A. Pugžlys, G. Andriukaitis, E. A. Stepanov, S. Ališauskas, T. Flöri, A. B. Fedotov, V. Y. Panchenko, A. Baltuška, and A. M. Zheltikov, “Subterawatt femtosecond pulses in the mid-infrared range: new spatiotemporal dynamics of high-power electromagnetic fields,” Phys.-Usp. 58(1), 89–94 (2015). [CrossRef]
22. A. Lyachev, I. O. Musgrave, Y. Tang, C. Hernandez-Gomez, I. N. Ross, M. Galimberti, O. V. Chekhlov, and J. Collier, “Development of a novel large bandwidth front-end system for high peak power OPCPA systems,” Opt. Express 19(17), 15824–15832 (2011). [CrossRef]
23. V. Lozhkarev, G. Freidman, V. Ginzburg, et al., “200 TW 45 fs laser based on optical parametric chirped pulse amplification,” Opt. Express 14(1), 446–454 (2006). [CrossRef]
24. G. Andriukaitis, T. Balčiūnas, S. Ališauskas, A. Pugžlys, A. Baltuška, T. Popmintchev, M.-C. Chen, M. M. Murnane, and H. C. Kapteyn, “90 GW peak power few-cycle mid-infrared pulses from an optical parametric amplifier,” Opt. Lett. 36(15), 2755–2757 (2011). [CrossRef]
25. Z. Heiner, V. Petrov, G. Steinmeyer, M. J. J. Vrakking, and M. Mero, “100-khz, dual-beam opa delivering high-quality, 5-cycle angular-dispersion-compensated mid-infrared idler pulses at 3.1 µm,” Opt. Express 26(20), 25793–25804 (2018). [CrossRef]
26. R. Budriūnas, T. Stanislauskas, J. Adamonis, A. Aleknavičius, G. Veitas, D. Gadonas, S. Balickas, A. Michailovas, and A. Varanavičius, “53 W average power CEP-stabilized OPCPA system delivering 5.5 TW few cycle pulses at 1 kHz repetition rate,” Opt. Express 25(5), 5797–5806 (2017). [CrossRef]
27. S. Witte, R. T. Zinkstok, A. L. Wolf, W. Hogervorst, W. Ubachs, and K. S. E. Eikema, “A source of 2 terawatt, 2.7 cycle laser pulses based on noncollinear optical parametric chirped pulse amplification,” Opt. Express 14(18), 8168–8177 (2006). [CrossRef]
28. S. Adachi, H. Ishii, T. Kanai, N. Ishii, A. Kosuge, and S. Watanabe, “1.5 mJ, 6.4 fs parametric chirped-pulse amplification system at 1 kHz,” Opt. Lett. 32(17), 2487–2489 (2007). [CrossRef]
29. D. Herrmann, L. Veisz, R. Tautz, F. Tavella, K. Schmid, V. Pervak, and F. Krausz, “Generation of sub-three-cycle, 16 TW light pulses by using noncollinear optical parametric chirped-pulse amplification,” Opt. Lett. 34(16), 2459–2461 (2009). [CrossRef]
30. Y. Deng, A. Schwarz, H. Fattahi, M. Ueffing, X. Gu, M. Ossiander, T. Metzger, V. Pervak, H. Ishizuki, T. Taira, T. Kobayashi, G. Marcus, F. Krausz, R. Kienberger, and N. Karpowicz, “Carrier-envelope-phase-stable, 1.2 mJ, 1.5 cycle laser pulses at 2.1 μm,” Opt. Lett. 37(23), 4973–4975 (2012). [CrossRef]
31. K. Zhao, H. Zhong, P. Yuan, G. Xie, J. Wang, J. Ma, and L. Qian, “Generation of 120 GW mid-infrared pulses from a widely tunable noncollinear optical parametric amplifier,” Opt. Lett. 38(13), 2159–2161 (2013). [CrossRef]
32. Y. Yin, J. Li, X. Ren, K. Zhao, Y. Wu, E. Cunningham, and Z. Chang, “High-efficiency optical parametric chirped-pulse amplifier in BiB3O6 for generation of 3 mJ, two-cycle, carrier-envelope-phase-stable pulses at 1.7 μm,” Opt. Lett. 41(6), 1142–1145 (2016). [CrossRef]
33. A. Kessel, V. E. Leshchenko, O. Jahn, M. Krüger, A. Münzer, A. Schwarz, V. Pervak, M. Trubetskov, S. A. Trushin, F. Krausz, Z. Major, and S. Karsch, “Relativistic few-cycle pulses with high contrast from picosecond-pumped OPCPA,” Optica 5(4), 434–442 (2018). [CrossRef]
34. J. Bromage, S.-W. Bahk, I. A. Begishev, et al., “Technology development for ultraintense all-OPCPA systems,” High Power Laser Sci. Eng. 7, e4 (2019). [CrossRef]
35. J. Bromage, S.-W. Bahk, M. Bedzyk, et al., “MTW-OPAL: a technology development platform for ultra-intense optical parametric chirped-pulse amplification systems,” High Power Laser Sci. Eng. 9, e63 (2021). [CrossRef]
36. I. A. Begishev, V. Bagnoud, S.-W. Bahk, et al., “Advanced laser development and plasma-physics studies on the multiterawatt laser,” Appl. Opt. 60(36), 11104–11124 (2021). [CrossRef]
37. V. G. Dmitriev, G. G. Gurzadyan, and D. N. Nikogosyan, Handbook of Nonlinear Optical Crystals (Springer, 1991), p. 78.
38. Fastlite, Pôle Euro - Bâtiment D, 165 rue des Cistes, 06600 Antebes, France.
39. V. Bagnoud, M. J. Guardalben, J. Puth, J. D. Zuegel, T. Mooney, and P. Dumas, “High-energy, high-average-power laser with Nd:YLF rods corrected by magnetorheological finishing,” Appl. Opt. 44(2), 282–288 (2005). [CrossRef]
40. Š. Vyhlídka, D. Kramer, G. Kalinchenko, and B. Rus, “Seidel aberrations in grating pulse stretchers,” Opt. Express 24(26), 30421–30432 (2016). [CrossRef]
41. F. A. Jenkins and H. E. White, Fundamentals of Optics (McGraw-Hill Primis Custom Publishing, 2001).
42. Z. Bor, “Distortion of femtosecond laser pulses in lenses,” Opt. Lett. 14(2), 119–121 (1989). [CrossRef]
43. APE angewandte physik & elektronick GmbH, “Ultrafast Laser Diagnostics & Tuneable Laser Solutions,” Berlin, Germany.
44. L. Rahimi, M. Abedi, A. A. Askari, and H. Saghafifar, “Optimal design of a grism-pair for simultaneous second-, third-, and fourth-order dispersion compensating in chirped-pulse amplification,” Appl. Phys. B: Lasers Opt. 123(6), 177 (2017). [CrossRef]
45. N. Forget, S. Grabielle, and P. Tournois, “Tilted transmission grisms for pulse compression with dispersion control up to the fourth order,” in CLEO (Optical Society of America, 2014), paper SW1E.6.
46. J. Tan, N. Forget, A. Borot, D. Kaplan, P. Tournois, A. Muschet, and L. Veisz, “Dispersion control for temporal contrast optimization,” Opt. Express 26(19), 25003–25012 (2018). [CrossRef]
47. I. Ross, P. Matousek, M. Towrie, A. Langley, and J. Collier, “The prospects for ultrashort pulse duration and ultrahigh intensity using optical parametric chirped pulse amplifiers,” Opt. Commun. 144(1-3), 125–133 (1997). [CrossRef]
