Widely tunable femtosecond fiber optical parametric oscillator

The phase-matching condition in a fiber is discussed. A balance among the different orders of fiber dispersion can be found to achieve a widely tuning modulation instability gain for pumping around the normal dispersion regime. Three coupled nonlinear wave equations are used to simulate the femtosecond fiber optical parametric oscillator. The numerical results show that, through appropriate choice of dispersion, femtosecond pulses with a 180-nm tunable range can be generated when pump wavelength near a fiber’s zero-dispersion wavelength is tuned only 7 nm. Further tuning is limited by the walk-off between the pump and the signal pulses.     

Widely tunable photonic crystal fiber Fabry-Perot optical parametric oscillator

We present a widely tunable low-threshold chi(3) optical parametric oscillator. The oscillator cavity is formed by butt coupling dichroic mirrors to either end of a highly nonlinear index-guiding photonic crystal fiber. This yields a singly resonant Fabry-Perot oscillator with a high feedback fraction for the resonant parametric sideband. The tuning range of the output parametric sideband stretches from 23 to 164 THz above the pump frequency. The threshold power of the oscillator is only 15 W.     

Improved efficiency of a pulsed optical parametric oscillator by delayed double-pass pump

By delaying the second pass of the pump of a singly resonant optical parametric oscillator, the conversion efficiency can be improved. We show the experimental results of an intracavity-doubled singly resonant parametric oscillator pumped by a Q-switched laser. Using 0.49 mJ of pump energy at 532 nm from a diode-pumped Nd:YAG laser, 0.085 mJ of 488 nm was obtained with the optimum delay for the second pass of the pump, giving a conversion efficiency of 17%. The improvement over the case of a single-pass pump was 85%, and the improvement over the double-pass pump with a small delay was 40%.     

Pump-enhanced optical parametric oscillator generating continuous wave tunable terahertz radiation

We demonstrate a tunable cw terahertz (THz) parametric oscillator based on periodically poled MgO-doped lithium niobate, directly converting the 1030 nm pump wave into the THz regime. The tunability ranges from 1.2 to 2.9 THz at output power levels between 0.3 and 3.9 μW. To overcome the high pump threshold caused by THz absorption in the nonlinear crystal, we employ an enhancement cavity with a finesse of 500 at the pump wavelength. The intracavity pump threshold at 1.4 THz is measured to be 350 W for a crystal length of 2.5 cm.     

Multiwatt level output powers from a tunable fiber optical parametric oscillator

We present an all-fiber high average power fiber optical parametric oscillator based on standard telecommunications dispersion-shifted fiber. The output of the oscillator is continuously tunable out to ±28 THz from the pump wavelength. The average power of the oscillator's output is in excess of 1.9?W in each sideband out to ±25 THz detuning. Between 5 and 14 THz detuning, the average power of the Stokes output is in excess of 3.8 W.     

Rapidly tunable continuous-wave optical parametric oscillator pumped by a fiber laser

We report on rapid, all-electronically controlled wavelength tuning of a continuous-wave (cw) optical parametric oscillator (OPO) pumped by an ytterbium fiber laser. The OPO is singly resonant for the signal wave and consists of a 40-mm-long periodically poled lithium niobate crystal in a four-mirror ring cavity. By tuning of the fiber-laser wavelength over 33 nm through an intracavity acousto-optic tunable filter, the OPO idler wavelength is tuned from 3160 to 3500 nm in 330 micros, corresponding to an idler frequency-tuning speed of 28 THz/ms. At a fiber-laser power of 6.6 W at 1074 nm, the singly resonant OPO generates 1.13-W cw idler radiation at 3200 nm.     

Continuous-wave fiber optical parametric oscillator

We report continuous-wave operation of singly resonant fiber optical parametric oscillators. In a cavity formed by 100 m of highly nonlinear fiber and two fiber Bragg gratings, the pump power threshold was 240 mW; the output wavelength could be tuned over 80 nm by tuning of the pump. We also obtained an internal conversion efficiency of 30%, compared with the maximum theoretical value of 50%, by use of a 1-km-long cavity.     

Wavelength-spacing tunable multi-wavelength fiber optical parametric oscillator based on multiple four-wave mixing

We propose a wavelength-spacing tunable multi-wavelength fiber optical parametric oscillator (MW-FOPO) with a simple line cavity and one pump source based on multiple four-wave mixing (MFWM). Stable multi-wavelength lasing at room temperature is achieved due to the four-wave mixing effect and the broadband gain of the fiber optical parametric amplifier based on a highly nonlinear fiber. The wavelength spacing of the proposed MW-FOPO can be tuned by adjusting the wavelength of the pump light or the central wavelength of the fiber Bragg grating. Seventeen lasing lines with a wavelength spacing of 2.89 nm and an extinction ratio larger than 10 dB, which covers the wavelength region from 1540 to 1568 nm is demonstrated.     

Widely tunable single-frequency pulsed optical parametric oscillator

The spectral output of a nanosecond dual-cavity doubly resonant optical parametric oscillator has been investigated versus the relative length of the signal and idler cavities. Regions of stable single-frequency operation are determined by use of a type II phase-matched KTP crystal and compared with the predictions of a mode-overlap model. A wide mode-hop-free tuning range is obtained over 40 GHz, limited only by piezoelectric biases. Furthermore, discrete tuning is investigated over the full parametric gain curve. For demonstration purposes, experiments are performed in the domain that is most inclined to multifrequency emission, i.e., near degeneracy.     

Widely tunable optical parametric oscillator with electrical wavelength control

A LiNbO(3) optical parametric oscillator (OPO) pumped at 930nm shows a wide phase-matching curve. Each pulse produced by the OPO has a very broad natural linewidth, from 1480 to 1800 nm for the signal and from 1950 to 2550 nm for the idler. The emission wavelength is controlled thanks to an electrically tunable Fabry-Perot interferometer inserted into the OPO cavity. The signal wavelength is electrically tuned in the range 1450-1850nm without crystal rotation.     

Broadly tunable noncritically phase-matched ZnGeP2 optical parametric oscillator with a 2-microJ pump threshold

We report a high-repetition-rate (1-10-kHz) optical parametric oscillator (OPO) based on noncritically phase-matched ZnGeP2 (ZGP). The pump source was an OPO based on periodically pole lithium niobate that was pumped in turn by a Q-switched diode-pumped 1-microm Nd:YAG laser. The ZGP OPO yielded continuously tunable output from 3.7 to 10.2 microm by tuning of the pump wavelength from 2.3 to 3.7 microm. At the optimal pump focusing, the minimum ZGP OPO threshold achieved was 2 microJ, which is to our knowledge the lowest ever reported for a singly resonant OPO. The output energy in the 6-8-microm range was > 20 microJ, and the quantum efficiency of converting 1-microm radiation to the mid IR exceeded 10%.     

Continuous wave optical parametric oscillator for quartz-enhanced photoacoustic trace gas sensing

A continuous wave optical parametric oscillator, generating up to 300 mW idler output in the 3–4 μm wavelength region, and pumped by a fiber-amplified DBR diode laser is used for trace gas detection by means of quartz-enhanced photoacoustic spectroscopy (QEPAS). Mode-hop-free tuning of the OPO output over 5.2 cm^-1 and continuous spectral coverage exceeding 16.5 cm^-1 were achieved via electronic pump source tuning alone. Online monitoring of the idler wavelength, with feedback to the DBR diode laser, provided an automated closed-loop control allowing arbitrary idler wavelength selection within the pump tuning range and locking of the idler wavelength with a stability of 1.7×10^-3 cm^-1 over at least 30 min. Using this approach, we locked the idler wavelength at an ethane absorption peak and obtained QEPAS data to verify the linear response of the QEPAS signal at different ethane concentrations (100 ppbv-20 ppmv) and different power levels. The detection limit for ethane was determined to be 13 ppbv (20 s averaging), corresponding to a normalized noise equivalent absorption coefficient of 4.4×10^-7 cm^-1  W/Hz^1/2. PACS 42.55.Wd; 42.65.Yj; 42.62.Fi     

宽调谐高效率的BBO光参量振荡器

本文报道用354.7nm泵浦的单共振BBO脉冲光参量振荡器在413～661nm和2513～765nm波段内获得了可调谐的振荡输出,最高总能量转换效率达52％;文中还讨论了输出特性。     

Continuous wave monolithic quasi-phase-matched optical parametric oscillator in periodically poled lithium niobate

We demonstrate a monolithic and quasi-phasematched singly resonant cw optical parametric oscillator in periodically poled lithium niobate. The threshold is 1.0 W and the OPO delivers up to 0.98 W signal power tunable between 1750 and 1950 nm (2710 and 2340 nm idler, respectively). We identify cascaded parasitic oscillation effects and analyze their behavior theoretically, showing good agreement with our experiment. The analysis of parasitic effects points the way to improved device designs that should enable stable, compact, and frequency-tunable sources.     

High-efficiency nanosecond optical parametric oscillator with the stable ring configuration

High stability nanosecond OPO operation at 1.57 μm was realized based on the type II non-critically phase-matched (NCPM) KTP crystal by utilizing a single frequency Nd:YAG master oscillator power amplifier (MOPA) laser as pump source. Energy conversion efficiency of 18.1% was demonstrated with single-pass ring cavity which was approximately two times more than that of critical ring cavity. The highest slope efficiency of 37.76% and maximum signal pulse energy of 3.1 mJ were attained with the output reflectivity of R = 50% at the pulse repetition frequency of 100 Hz. Experimental results reveal that the nanosecond OPO with ring stable configuration is a promising design to meet the need of IPDA’s transmitter.     

High conversion efficiency fiber optical parametric oscillator

We present a χ(3) fiber parametric oscillator with high conversion efficiency from the input pump wave to the output parametric sidebands. By introducing an intracavity filter detuned from the oscillator's phase-matched frequency conversion efficiencies considerably higher than those possible when operating at the phase-matched frequency are demonstrated. Experimentally we are able to obtain a total internal conversion efficiency in excess of 93% from the pump to the Stokes and anti-Stokes sidebands.     

可调谐PPLN中红外光参量振荡器失调特性

 通过对晶体进行周期调谐,实现了中红外参量光输出,在此基础上研究了晶体移动、腔镜偏转等对失调特性的影响。结果表明：由于PPLN通道的小尺寸波导特性和参量振荡特性,其失调特性不同于常规激光器。PPLN晶体沿不同轴移动的功率变化曲线有不同的特点,沿x轴移动的失调容限大于沿y轴移动的失调容限;腔镜的失调容限与腔镜偏转方向有关,腔镜横向偏转的失调容限大于纵向偏转的失调容限;PPLN晶体温度和通道对失调容限几乎没有影响。     

可调谐PPLN中红外光参量振荡器失调特性

通过对晶体进行周期调谐,实现了中红外参量光输出,在此基础上研究了晶体移动、腔镜偏转等对失调特性的影响。结果表明：由于PPLN通道的小尺寸波导特性和参量振荡特性,其失调特性不同于常规激光器。PPLN晶体沿不同轴移动的功率变化曲线有不同的特点,沿x轴移动的失调容限大于沿y轴移动的失调容限;腔镜的失调容限与腔镜偏转方向有关,腔镜横向偏转的失调容限大于纵向偏转的失调容限;PPLN晶体温度和通道对失调容限几乎没有影响。     

GaAs optical parametric oscillator with circularly polarized and depolarized pump

We demonstrate an optical parametric oscillator (OPO) based on GaAs pumped with linearly polarized and circularly polarized light and show that the relative OPO thresholds agree with theoretical expectations. For the circularly polarized pump, the threshold was as low as for the [111]-linearly polarized pump case. The pump was also passed through a Lyot depolarizer to produce pseudo-depolarized light, and the OPO threshold in this case was only 22% higher than that for [001]-linearly polarized pump.     

Broadly tunable femtosecond parametric oscillator using a photonic crystal fiber

Pulses as short as 460 fs and a tuning range as wide as 200 nm around 1 microm have been achieved from a photonic-crystal-fiber-based parametric oscillator. The ring cavity with only 65 cm of photonic crystal fiber is synchronously pumped with a tunable passively mode-locked Yb-doped fiber laser. Widely extended tunability is achieved by using the modulation instability gain in normal dispersion as the result of high-order dispersion in the photonic crystal fiber.