Picosecond Optical Parametric Generation Research Articles

2.76–3.98 μm picosecond mid-infrared optical parametric generation in a muti-grating MgO: PPLN

The high repetition rate, widely tunable, picosecond mid-infrared laser plays an important role in various fields. In this paper, the single-pass optical parametric generator (OPG) pumped by Yb-fiber laser based on MgO: PPLN is proposed. The Yb-fiber laser is mode locked by a nonlinear amplifying loop mirror (NALM) with an all-polarization-maintaining (PM) structure. A maximum power of 6.2 W was obtained with a repetition rate of 15.8 MHz and pulse duration of 18 ps after amplification by cascaded fiber. Based on the principle of nonlinear frequency down-conversion, the tunable mid-infrared output wavelength of 2.76–3.98 μm was realized by varying the crystal grating periods and temperature. The maximum power was 500 mW at 3.22 μm, corresponding to a quantum conversion efficiency of 25%, and the relative power fluctuation was measured as 0.37% over 30 min.

Combined parametric down‐ and up‐conversion noncollinear processes under picosecond pumping in KTP, controlled by injection seeding

AbstractA cascade mechanism of the emerging of a radiation in blue and red spectral ranges in the KTP crystal—combined non‐collinear parametric down‐ and up‐conversion—was discovered and experimentally investigated. To become observable this mechanism needs to be accompanied by a process of parametric amplification of the seeding wave. The non‐collinear optical parametric amplifier based on the KTP crystal, pumped by 532 nm picosecond pulses, was exploited to study combined noncollinear down‐conversion and up‐conversion processes. Narrowband seeding was provided by radiation of a picosecond optical parametric generator pumped by 355‐nm picosecond pulses synchronized with 532‐nm pulses. The corresponding phase matching conditions for both down‐ and up‐conversion stages were found out on the basis of the tuning curves calculated for the type II phase matching in the XOZ plane of the KTP crystal. When the wavelength and noncollinearity angle of the seeding matched any signal wave of the down‐conversion stage, the seeding was amplified. Along with this, a radiation appeared in the visible part of the spectrum, which was not observed without seeding amplification. The wavelengths and spatial patterns of the radiation arisen, corresponded to some phasematched processes of sum frequency generation between the signal and idler waves existing in the crystal at the down‐conversion stage. Being very weak, these processes are usually unobserved. Thus, injection seeding allows from plenty possible processes to reveal and highlight only those, which correspond to the noncollinearity angle and the wavelength of the seeding. This phenomenon potentially can be exploited to control light at the outlet of a nonlinear crystal.

Performance studies of high-average-power picosecond optical parametric generation and amplification in MgO:PPLN at 80 MHz.

We report on performance studies of high-average-power single-pass picosecond optical parametric generation (OPG) and amplification (OPA) tunable near 2 µm in MgO:PPLN pumped by an Yb-fiber laser at 1.064 µm and 80 MHz pulse repetition rate. The simple setup based on two identical crystals, and without the need for an intermediate delay line for synchronization, delivers up to 6.3 W of average power at an overall conversion efficiency of ∼50% and is tunable across 1902-2415 nm. We present systematic characterization of OPG and OPA stages to compare their performance and investigate the effect of parametric generation in the high-gain limit, enabling high output power and full-width-half-maximum (FWHM) spectral bandwidths as large as 189 nm. The OPG-OPA output exhibits excellent passive power stability better than 0.3% rms and central wavelength stability better than 0.03% rms over 1 hour, in high spatial beam quality with M2<2. The OPG output pulses have duration of 5.2 ps with a FWHM spectral bandwidth of 117 nm at 2123 nm, resulting in a time-bandwidth product of ΔτΔν∼40, indicating ∼4 times temporal compression compared to the input pump pulses. Theoretical simulations confirm the effect of pump beam divergence on the observed shift in wavelength tuning with respect to temperature, while the exponential gain in the parametric process is identified as playing a key role in the resulting pulse compression.

Fiber-laser-pumped high-repetition-rate picosecond optical parametric generation and amplification in MgO:PPLN.

We report the generation of tunable high-repetition-rate picosecond pulses in the near-infrared at high average power with record conversion efficiency using single-pass optical parametric generation (OPG) and amplification (OPA) in MgO:PPLN, for the first time, to the best of our knowledge. By deploying a mode-locked Yb-fiber laser at 1064 nm providing 21 ps pump pulses at 80 MHz, and a cascade of two 50-mm-long MgO:PPLN crystals, we generate up to 8.3 W of total average output power at a conversion efficiency of 59% over a tunable range of 513 nm, across 1902-2415 nm, with a record threshold as low as 600 mW (7.5 nJ). The two-stage OPG-OPA scheme provides control over fine wavelength tuning and output spectral bandwidths, enabled by the independent control of phase-matching in each crystal. The OPG-OPA output exhibits high spatial beam quality and excellent passive power and central wavelength stability better than 0.9% rms and 0.1% rms, respectively, over 1 hour. The output pulses have a duration of ∼11ps, with a 10 dB bandwidth of ∼350nm at 2107 nm.

Picosecond optical parametric generator and amplifier for large temperature-jump.

An optical parametric generator and amplifier producing 15 ps pulses at wavelengths tunable around 2 μm, with energies up to 15 mJ/pulse, has been realized and characterized. The output wavelength is chosen to match a vibrational combination band of water. By measuring the induced birefringence changes we prove that a single pulse is able to completely melt samples of ice in the 10⁻⁶ cm³ volume range, both at room pressure (263 K) and at high pressure (298 K, 1 GPa) in a sapphire anvil cell. This source opens the possibility of studying melting and freezing processes by spectroscopic probes in water or water solutions in a wide range of conditions as found in natural environments.

High Energy Picosecond Optical Parametric Amplifier Pumped by the Second Harmonic of a Two-Stage Ti:sapphire Laser

We demonstrate a high energy picosecond optical parametric generation and amplification (OPA) system in the visible range based on two type-I phase matched β-barium borate crystals, in a walk-off compensating geometry. The second harmonic of a two-stage 60 ps Ti:sapphire laser amplifier at 10 Hz repetition rate serves as the pump. The signal is continuously tunable from 460 to 750 nm, which covers most of the visible range. The corresponding tuning range in the idler branch is from 0.86 to 3.07 μm. At a pumping energy of 110 mJ per pulse, the signal pulse energy is at 20 mJ class for most of the tuning wavelength in the OPA stage, and reaches a maximum of 33 mJ at 710 nm, corresponding to a conversion efficiency of ~ 30%.

Tunable, high-energy, mid-infrared, picosecond optical parametric generator based on CdSiP_2

We report a tunable, high-energy, single-pass optical parametric generator (OPG) based on the nonlinear material, cadmium silicon phosphide, CdSiP(2). The OPG is pumped by a cavity-dumped, passively mode-locked, diode-pumped Nd:YAG oscillator, providing 25 µJ pulses in 20 ps at 5 Hz. The pump energy is further boosted by a flashlamp-pumped Nd:YAG amplifier to 2.5 mJ. The OPG is temperature tunable over 1263-1286 nm (23 nm) in the signal and 6153-6731 nm (578 nm) in the idler. Using the single-pass OPG configuration, we have generated signal pulse energy as high as 636 µJ at 1283 nm, together with idler pulse energy of 33 µJ at 6234 nm, for 2.1 mJ of input pump pulse energy. The generated signal pulses have durations of 24 ps with a FWHM spectral bandwidth of 10.4 nm at central wavelength of 1276 nm. The corresponding idler spectrum has a FWHM bandwidth of 140 nm centered at 6404 nm.

Generation of broadly tunable picosecond mid-infrared laser and sensitive detection of a mid-infrared signal by parametric frequency up-conversion in MgO:LiNbO3 optical parametric amplifiers

Picosecond optical parametric generation and amplification in the near-infrared region within 1.361–1.656 μm and the mid-infrared region within 2.976–4.875 μm is constructed on the basis of bulk MgO:LiNbO3 crystals pumped at 1.064 μm. The maximum pulse energy reaches 1.3 mJ at 1.464 μm and 0.47 mJ at 3.894 μm, corresponding to a pump-to-idler photon conversion efficiency of 25%. By seeding the hard-to-measure mid-infrared radiation as the idler in the optical parametric amplification and measuring the amplified and frequency up-converted signal in the near-infrared or even visible region, one can measure very week mid-infrared radiation with ordinary detectors, which are insensitive to mid-infrared radiation, with a very high gain. A maximum gain factor of about 7 × 107 is achieved at the mid-infrared wavelength of 3.374 μm and the corresponding energy detection limit is as low as about 390 aJ per pulse.

Dual-frequency picosecond optical parametric generator pumped by a Nd-doped vanadate bounce laser

Dual-frequency MHz-repetition 1.5-μm optical parametric generation is demonstrated from a tandem system pumped by a picosecond Nd:YVO₄ bounce laser. An average power of 1.0 W is obtained over the range 1571-1630 nm, corresponding to an optical-optical conversion efficiency and slope efficiency of 16% and 23%, respectively. Terahertz-wave with a frequency of 3.2 THz is also generated from the system in combination with an organic nonlinear DAST crystal.

Development of a nearly transform-limited, low-repetition-rate, picosecond optical parametric generator

A low-repetition-rate (10-Hz), picosecond (ps) optical parametric generator (OPG) seeded at the idler wavelength with a high-power diode laser is demonstrated. The output of the OPG at ∼566 nm is amplified in dye cells, resulting in signal enhancement by more than three orders of magnitude. The nearly transform-limited beam at ∼566 nm has a pulsewidth of ∼170 ps, with an overall output of ∼2.3 mJ/pulse. The laser is tuned either by tuning the nonlinear crystal or the seed-laser current. The applications of such a simple, compact, high-performance, tunable ps laser system for linear and nonlinear spectroscopies are outlined.

Widely tunable picosecond optical parametric generation and amplification in BiB3O6

Efficient generation of widely tunable picosecond pulses from the visible to near-infrared is demonstrated by optical parametric generation and amplification in BiB(3)O(6). Pumped by the second harmonic of an amplified mode-locked Nd:YAG laser at 532 nm, also generated in BiB(3)O(6), a signal and idler tuning range of 740-1893 nm has been achieved with angle tuning under type I (o?e+e) phase-matching in the optical yz-plane. With 40-ps pump pulses of 420-muJ energy, single-pass signal pulse energies of up to 48.6 muJ have been obtained at total OPA pump to signal and idler conversion efficiency as high as 30%. Significant temperature tuning under type I (o?e+e) noncritical interaction along the optical z-axis is also demonstrated, extending the signal tuning range from 740 nm down to 676 nm and idler tuning range from 1893 nm up to 2497 nm. Using second harmonic generation of the amplified signal pulses, also in BiB(3)O(6),wavelength extension to 370-500 nm has been achieved at 24% conversion efficiency, providing 10-muJ pulses across the tuning range. Optical parametric generation and amplification in BiB(3)O(6) under strong two-photon absorption pumped by 210-muJ pulses at 355 nm is also reported, providing amplified signal pulse energies of 14.2 muJ at OPA conversion efficiency as high as 21% and a spectral coverage across 450-1674 nm.

Blue Light Tuning Output of Picosecond Optical Parametric Generation and Amplification in Intelligent Controller

A blue light 420–485 nm output with a linewidth of 0.3 nm and a pump-to-signal energy conversion efficiency of up to 29% at an injected seeding energy of 400 µJ has been achieved. The optimum crystal length from 4 to 2 mm at a pump intensity of 500 MW/cm2 is studied using computer simulation. The experimental designs of the optical parametric generation of type-II noncritical-phase-matched LiB3O5 and the amplification of type-I critical-phase-matched β-BaB2O4 are presented in detail. The experimental setup is pumped using the 355 nm 30 ps-duration output pulse of an active-passive model-locked Nd:YAG laser, is reported.

Picojoule threshold, picosecond optical parametric generation in reverse proton-exchanged lithium niobate waveguides

We have demonstrated picosecond optical parametric generation in reverse proton-exchanged waveguides in periodically poled lithium niobate with thresholds as low as 200 pJ. Near-transform-limited near-infrared pulses were obtained from cascaded optical parametric generation. For a 1.8-ps (FWHM) pump pulse at 769.6 nm, a saturated internal photon-conversion efficiency of 33% was obtained with 1 nJ of pump energy. The signal-wavelength tuning range was from 1.15 μm to 2.3 μm with a pump wavelength between 770 nm and 789.5 nm. Numerical simulations well predicted the mechanism for the transform-limited pulse generation. These results enable optical parametric generation devices with low threshold and good temporal properties with a simple single-pass setup.

A 9.5-W 82-MHz-repetition-rate picosecond optical parametric generator with cw diode laser injection seeding

We report on an injection-seeded 9.5-W 82-MHz-repetition-rate picosecond optical parametric generator (OPG) based on a 55 mm long crystal of periodically poled lithium niobate (PPLN) with a quasi-phase-matching (QPM) grating period of 29.75 μm. The OPG is excited by a continuously diode pumped mode-locked picosecond Nd:YVO4 oscillator-amplifier system. The laser system generates 7 ps pulses with a repetition rate of 82.3 MHz and an average power of 24 W. Without injection-seeding the total average output power of the OPG is 8.9 W, which corresponds to an internal conversion efficiency of 50%. The wavelengths of the signal and idler waves were tuned in the range 1.57–1.64 μm and 3.03–3.3 μm, respectively, by changing the crystal temperature from 150 °C to 250 °C. Injection seeding of the OPG at 1.58 μm with 4 mW of single frequency continuous-wave radiation of a distributed-feedback (DFB) diode laser increases the OPG output to 9.5 W (53% conversion efficiency). The injection seeding increases the pulse duration and reduces the spectral bandwidth. When pumped by 10 W of 1.06 μm laser radiation, the duration of the signal pulses increased from 3.6 ps to 5.5 ps while the spectral bandwidth is reduced from 4.5 nm to 0.85 nm. Seeding thus improved the time-bandwidth product from 1.98 to a value of 0.56, much closer to the Fourier limit.

Angular structure formation in single-pass optical parametric generators pumped by intersecting beams

Investigation results of angular structure formation in a picosecond traveling-wave optical parametric generator (OPG) based on a KDP crystal (type II phase matching) pumped by intersecting beams are presented. It is demonstrated that the angular structure of the OPG output radiation is controlled by pump geometry. Frequency-tuned diffraction-limited output even in a single-pass OPG was observed.

Parametric gain of the generation and the amplification of ultrashort optical pulses

A theoretical model for calculating the effective gain of parametric generation and amplification of ultrashort optical pulses is presented. This model takes into account both spatial and temporal effects, including spatial beam broadening, temporal pulse broadening, spatial walk-off of the pulse beams, and temporal walk-off of the parametrically interacting pulses. An analytical formulation for the parametric efficiency coefficient and the effective gain in terms of six spatial and temporal characteristic lengths is obtained. This formulation allows for an easy evaluation of the threshold and the efficiency of a synchronously pumped optical parametric oscillator generating ultrashort pulses without requiring the solution of a differential equation. It can also be used to calculate the amplification factor and the output pulse energy in parametric amplification and difference-frequency generation of ultrashort pulses. Numerical results for picosecond and femtosecond optical parametric generation and amplification in the KTP crystal are presented for many different experimental conditions.

Kilohertz all-solid-state picosecond lithium triborate optical parametric generator

An all-solid-state picosecond optical parametric generation system that uses a single-pass noncritically phase-matched lithium triborate crystal is demonstrated. We have achieved > 20% total conversion from lambda = 532 nm (pump) to lambda = 800 nm (signal) and 1.6 microm (idler) with a pulse width of ~15 ps and average power of 200 mW at a repetition rate of 3 kHz (~50 microJ/signal pulse). Frequency tuning from <750 nm to >1.8 microm is achieved by temperature tuning of the lithium triborate.

Picosecond optical parametric generation and amplification in LiB3O5 and β-BaB2O4

In this letter, an optical parametric generation and amplification system including a type II noncritically phase-matched LiB3O5 and a type I critically phase-matched β-BaB2O4 is reported. Pumped by 4.8 mJ 30 ps 355 nm laser pulse, 415.9–482.6 nm tunable wavelengths with linewidths as low as 0.15 nm have been obtained. System pump-to-signal energy conversion efficiency up to 32.7% with 1.57 mJ energy and 52 MW peak-power single pulse have been achieved.