Resonant Optical Parametric Oscillator Research Articles

种子注入双共振PPMgLN光参量振荡器

种子注入双共振PPMgLN光参量振荡器

内腔倍频单共振光学参量振荡器输出特性分析

内腔倍频单共振光学参量振荡器输出特性分析

Three-photon absorption in optical parametric oscillators based on OP-GaAs.

We report on, to the best of our knowledge, the first singly resonant (SR), synchronously pumped optical parametric oscillator (OPO) based on orientation-patterned gallium arsenide (OP-GaAs). Together with a doubly resonant (DR) degenerate OPO based on the same OP-GaAs material, the output spectra cover 3 to 6 μm within ∼3 dB of relative power. The DR-OPO has the highest output power reported to date from a femtosecond, synchronously pumped OPO based on OP-GaAs. We observed strong three-photon absorption with a coefficient of 0.35±0.08 cm³/GW² for our OP-GaAs sample, which limits the output power of these OPOs as mid-IR light sources. We present a detailed study of the three-photon loss on the performance of both the SR- and DR-OPOs, and compare them to those without this loss mechanism.

Wavelength tunable CW red laser generated based on an intracavity-SFG composite cavity

We report a wavelength-tunable watt-level continuous wave (CW) red laser that uses a composite cavity based on an intracavity sum-frequency generation (SFG). The composite cavity is composed of a LD side-pumped Nd: GdVO4 p-polarized 1062.9 nm resonant cavity and a resonant optical parametric oscillator (SRO) of s-polarized signal light using a periodically poled crystal MgO: PPLN. Based on the temperature tuning from 30 °C to 200 °C, the CW red laser beams are obtained in a tunable waveband from 634.4 nm to 649.1 nm, corresponding to a tunable output waveband from 3278.0 nm to 2940.2 nm of the mid-infrared idler lights. The maximum CW output power of the red laser at 634.4 nm and the idler light at 3278.0 nm reach 3.03 W and 4.13 W under 30 °C, respectively.

Fiber-laser-based, high-repetition-rate, picosecond ultraviolet source tunable across 329-348 nm.

We report a compact, fiber-laser-based, high-repetition-rate picosecond source for the ultraviolet (UV), providing multi-tens of milliwatt of average power across 329-348 nm. The source is based on internal sum-frequency-generation (SFG) in a singly resonant optical parametric oscillator (OPO), synchronously pumped at 532 nm by the second harmonic of a picosecond Yb-fiber laser at 80 MHz repetition rate. Using a 30-mm-long single-grating MgO:sPPLT crystal for the OPO and a 5-mm-long BiB3O6 crystal for intracavity SFG, we generate up to 115 mW of average UV power at 339.9 nm, with >50 mW over 73% of the tuning range, for 1.6 W of input pump power. The UV output exhibits a passive rms power stability of ∼2.9% rms over 1 min and 6.5% rms over 2 h in high beam quality. Angular acceptance bandwidth and cavity detuning effects have also been studied.

Yb-fiber laser pumped high-power, broadly tunable, single-frequency red source based on a singly resonant optical parametric oscillator.

We present an efficient and tunable source generating multi-watt single-frequency red radiation by intra-cavity frequency doubling of the signal in a MgO-doped periodically poled LiNbO3 (MgO:PPLN)-based singly resonant optical parametric oscillator (SRO). By optimally designing the SRO cavity in a six-mirror configuration, we generate ≈276 nm tunable idler radiation in mid-infrared with a maximum power of Pi=2.05 W at a pump power of Pp=14.0 W. The resonant signal is frequency doubled using a 10 mm-long BiB3O6 (BiBO) crystal which resulted in tunability of a red beam from ≈753 to 780 nm band with maximum power Pr≈4.0 W recorded at λr≈756 nm. The deployment of a six-mirror SRO ensures single-frequency generation of red across the entire tuning range by inducing additional losses to Raman modes of LiNbO3 and, thus, inhibiting their oscillation. Using a scanning Fabry-Perot interferometer (FPI), nominal linewidth of the red beam is measured to ≈3 MHz which changes marginally over the entire tuning range. Long-term (over 1 h) peak-to-peak frequency fluctuation of the generated red beam is estimated to be about 3.3 GHz under free-running conditions at Pp=14.0 W. The generated red beam is delivered in a TEM00 mode profile with M2≤1.32 at maximum power in a red beam.

Double resonant absorption measurement of acetylene symmetric vibrational states probed with cavity ring down spectroscopy.

A novel mid-infrared/near-infrared double resonant absorption setup for studying infrared-inactive vibrational states is presented. A strong vibrational transition in the mid-infrared region is excited using an idler beam from a singly resonant continuous-wave optical parametric oscillator, to populate an intermediate vibrational state. High output power of the optical parametric oscillator and the strength of the mid-infrared transition result in efficient population transfer to the intermediate state, which allows measuring secondary transitions from this state with a high signal-to-noise ratio. A secondary, near-infrared transition from the intermediate state is probed using cavity ring-down spectroscopy, which provides high sensitivity in this wavelength region. Due to the narrow linewidths of the excitation sources, the rovibrational lines of the secondary transition are measured with sub-Doppler resolution. The setup is used to access a previously unreported symmetric vibrational state of acetylene, ν1+ν2+ν3+ν4 (1)+ν5 (-1) in the normal mode notation. Single-photon transitions to this state from the vibrational ground state are forbidden. Ten lines of the newly measured state are observed and fitted with the linear least-squares method to extract the band parameters. The vibrational term value was measured to be at 9775.0018(45) cm(-1), the rotational parameter B was 1.162 222(37) cm(-1), and the quartic centrifugal distortion parameter D was 3.998(62) × 10(-6) cm(-1), where the numbers in the parenthesis are one-standard errors in the least significant digits.

Transient power characteristics of a compact singly resonant intracavity optical parametric oscillator pumped by a semiconductor disk laser

The multimode transient and steady state characteristics of a singly resonant intracavity optical parametric oscillator (ICSRO) pumped by a semiconductor disk laser have been numerically analyzed. Nonlinear parametric interaction in the ICSRO was shown to stimulate multimode lasing with an intensity dip at the central frequency of emission. The insertion of an etalon makes the device exhibit a single-mode operation.

Fourier transform and Vernier spectroscopy using an optical frequency comb at 3-5.4 μm.

We present a versatile mid-infrared frequency comb spectroscopy system based on a doubly resonant optical parametric oscillator tunable in the 3-5.4 μm range and two detection methods: a Fourier transform spectrometer (FTS) and a continuous-filtering Vernier spectrometer (CF-VS). Using the FTS with a multipass cell, we measure high precision broadband absorption spectra of CH4 at 3.3 μm and NO at 5.25 μm, the latter for the first time with comb spectroscopy, and we detect atmospheric species (CH4, CO, CO2, and H2O) in air in the signal and idler ranges. Multiline fitting yields minimum detectable concentrations of 10-20 ppb Hz-1/2 for CH4, NO, and CO. For the first time in the mid-infrared, we perform CF-VS using an enhancement cavity, a grating, and a single detector, and we measure the absorption spectrum of CH4 and H2O in ambient air at ∼3.3 μm, reaching a 40 ppb concentration detection limit for CH4 in 2 ms.

Joint Thermal Effects of VBG and Nonlinear Crystal in a Singly Resonant OPO

A continuous-wave singly resonant optical parametric oscillator employing a volume Bragg grating as one of the end mirrors is demonstrated. Due to the high intracavity power, the minute absorption of the grating leads to the thermal induced surface deformation and reflection peak shift. In this letter, the former effect is confirmed to be a cause of beam quality degradation of the resonant signal, while the latter, together with the thermal effects of the nonlinear crystal, leads to unconventional behaviors of power and stability. To the best of our knowledge, the joint effects of the grating and the nonlinear crystal are studied for the first time in details by changing the thermal effects of grating in varied strengths.

Optimal pump pulse shapes for optical parametric oscillators

In this paper we theoretically investigate the most efficient pump temporal shape for pulsed operation of optical parametric oscillators (OPOs). The theoretical analysis consists of solving the optimal control problem using the rate equation formalism. The OPO optimal buildup behavior is derived for any OPO configuration, and we show that the optimal pump pulse shape is a double rectangle. The first rectangle is optimized for the buildup process, while the second one is optimized for the steady state, and both depend differently on the OPO mirror reflectivities as well as the available pump energy and maximum peak power. This double rectangle is quantitatively described and is consistent with previous results reported in the literature. Also, numerical simulations are used to validate our analytical model on a doubly resonant OPO and show consistent results. The numerical simulations also show that an optimal top-hat temporal profile could provide performances very close to the ones achieved with the optimal double rectangle.

Amplified random fiber laser-pumped mid-infrared optical parametric oscillator

In this Letter, we report, for the first time to our knowledge, on a continuous-wave, singly resonant optical parametric oscillator using an MgO: PPLN crystal pumped by an all-fiberized master-oscillator power amplifier structured amplified random fiber laser. An idler output power of 2.46 W at 3752 nm is achieved with excellent beam quality, and the corresponding pump-to-idler conversion efficiency is 9.6% at room temperature. The idler output power exhibits a peak-to-peak power stability better than 12.7%, and the corresponding standard deviation is better than 3.6% RMS in about 20 min at the maximum output power. Meanwhile, other characteristics of the generated signal and idler laser are studied in detail and not only offered an effective guide in the research of optical parametric processes in the case of a continuous spectrum, but also broadened the range of random fiber laser applications.

Narrowing of the linewidth of an optical parametric oscillator by an acousto-optic modulator for the realization of mid-IR noise-immune cavity-enhanced optical heterodyne molecular spectrometry down to 10⁻¹⁰ cm⁻¹ Hz⁻¹/².

The linewidth of a singly resonant optical parametric oscillator (OPO) has been narrowed with respect to an external cavity by the use of an acousto-optic modulator (AOM). This made possible an improvement of the sensitivity of a previously realized OPO-based noise-immune cavity-enhanced optical heterodyne molecular spectrometry instrument for the 3.2 - 3.9 µm mid-infrared region by one order of magnitude. The resulting system shows a detection sensitivity for methane of 2.4 × 10(-10) cm(-1) Hz(-1∕2) and 1.3 × 10(-10) cm(-1) at 20 s, which allows for detection of both the environmentally important (13)CH(4) and CH(3)D isotopologues in atmospheric samples.

Telecom-heralded single-photon absorption by a single atom

We present, characterize, and apply a photonic quantum interface between the near infrared and telecom spectral regions. A singly resonant optical parametric oscillator (OPO) operated below threshold, in combination with external filters, generates high-rate ($>2.5\cdot10^6~{\rm s}^{-1}$) narrowband photon pairs ($\sim 7$ MHz bandwidth); the signal photons are tuned to resonance with an atomic transition in Ca$^+$, while the idler photons are at telecom wavelength. Quantum interface operation is demonstrated through high-rate absorption of single photons by a single trapped ion ($\sim 670~{\rm s}^{-1}$), heralded by coincident telecom photons.

High-efficiency PPMgLN-based mid-infrared optical parametric oscillator pumped by a MOPA-structured fiber laser with long pulse duration

We report our recent investigation on the conversion efficiency improvement of a PPMgLN-based single pump pass, singly resonant optical parametric oscillator (OPO) pumped by an acousto-optic Q-switched fiber MOPA. The impacts of the pump pulse duration and signal reflectivity on the pump-to-idler conversion efficiency were studied by numerically solving the coupled wave equations in the first place. The results revealed that longer pulse durations were beneficial to higher conversion efficiencies as long as the signal reflectivity of the OPO cavity was optimized accordingly. Experiments were carried out thereafter utilizing the optimal parameters obtained from the simulation. Idler powers of 4.7 and 3.81 W were achieved at 3.4 and 3.8 μm, respectively, under the highest pump power of 28 W with pump pulse duration of 240 ns. The experimental results were in good agreement with the calculated results. According to our simulation, higher conversion efficiency could be expected when such an OPO was pumped by pulses with even longer duration provided that the signal reflectivity of the output coupler was optimized under that pump condition.

Sub-kilohertz linewidth narrowing of a mid-infrared optical parametric oscillator idler frequency by direct cavity stabilization.

We stabilize the idler frequency of a singly resonant optical parametric oscillator directly to the resonance of a mid-infrared Fabry-Perot reference cavity. This is accomplished by the Pound-Drever-Hall locking scheme, controlling either the pump laser or the resonant signal frequency. A residual relative frequency noise power spectral density below 10(3) Hz(2)/Hz is reached on average, with a Gaussian linewidth of 920 Hz over 100 ms, which reveals the potential for reaching spectral purity down to the hertz level by locking the optical parametric oscillator against a mid-infrared cavity with state-of-the-art superior performance.

Few-cycle near-infrared pulses from a degenerate 1 GHz optical parametric oscillator.

We report the generation of transform-limited 4.3-cycle (23 fs) pulses at 1.6 μm from a degenerate doubly resonant optical parametric oscillator (OPO) pumped by a 1 GHz mode-locked Ti:sapphire laser. A χ(2) nonlinear envelope equation was used to inform the experimental implementation of intracavity group-delay dispersion compensation, resulting in resonant pulses with a 169 nm full width half-maximum spectral bandwidth, close to the bandwidth predicted by theory.

High-power, widely tunable, room-temperature picosecond optical parametric oscillator based on cylindrical 5%MgO:PPLN.

We report a high-power picosecond optical parametric oscillator (OPO) based on cylindrical MgO:PPLN synchronously pumped by an Yb-fiber laser. The singly resonant OPO is tunable in the near-infrared signal across 1413-1900 nm and mid-infrared idler over 2418-4307 nm by angle tuning of the crystal at room temperature. With non-optimized output coupling of ∼10%, the OPO simultaneously delivers 2.4 W of signal at 1664 nm and 1.7 W of idler at 2950 nm at an overall extraction efficiency of ∼45% with high beam-pointing stability <30 μrad and <14 μrad for the signal and idler, respectively. The generated signal and idler exhibit passive power stability better than 1% rms and 0.8% rms over 15 h, respectively, in high beam quality with TEM(00) profile. The extracted signal pulses from the OPO have duration of 15.2 ps with a spectral bandwidth of 0.7 nm, corresponding to a time-bandwidth product of ΔυΔτ∼1.2.

The influence of energy transfer upconversion on Q-switched single resonator optical parametric oscillator

The influence of energy transfer upconversion on Q-switched single resonator intracavity optical parametric oscillator is investigated by a space-dependent rate equation model. The numerical analysis shows that the energy transfer upconversion effect causes the pump size to have an optimum for yielding the largest output power at a given pump power. To verify the presented model, the practical example of Q-switched Nd : YVO4—KTA single resonator intracavity optical parametric oscillator has been used. The optimum pump size, calculated by presented model is 320 μm which is reported 300 μm.

Frequency stabilization of the non-resonant wave of a continuous-wave singly resonant optical parametric oscillator

We present an experimental technique allowing to stabilize the frequency of the non-resonant wave in a singly resonant optical parametric oscillator (SRO) down to the kHz level, much below the pump frequency noise level. By comparing the frequency of the non-resonant wave with a reference cavity, the pump frequency noise is imposed to the frequency of the resonant wave and is thus subtracted from the frequency of the non-resonant wave. This permits the non-resonant wave obtained from such a SRO to be simultaneously powerful and frequency stable, which is usually impossible to obtain when the resonant wave frequency is stabilized.