Cascaded synchronous terahertz optical parametric oscillations in a single MgO:PPLN crystal

We present a synchronously pumped optical parametric oscillator (OPO) based on a single MgO-doped periodically poled lithium niobate crystal (MgO:PPLN) delivering high-repetition-rate picosecond idler output in the mid-infrared. At high power levels, cascaded optical parametric oscillations are observed, from which the forward and backward idler waves are generated in the terahertz (THz) spectral region. We demonstrate the cascaded processes involving THz-wave generation and make explanations for the highorder cascaded optical parametric processes. The cascaded terahertz optical parametric oscillations in a synchronously pumped optical parametric oscillator are reported for the first time to the best of our knowledge.     

Phase-matched self-doubling optical parametric oscillator

We report a synchronously pumped intracavity frequency-doubled optical parametric oscillator that employs a single KTiOPO(4) crystal for both parametric generation and frequency doubling. Both nonlinear processes are phase matched for the same direction of propagation in the crystal. The parametric oscillator, pumped by a femtosecond Ti:sapphire laser at a wavelength of 745 nm, generates a green output beam at 540 nm with a 29% power conversion efficiency. Angle tuning in conjunction with pump wavelength tuning provides output tunability in the 530-585-nm range.     

Tunable fiber-optic parametric oscillator

We report operation of a tunable optical parametric oscillator that employs a nonlinear-fiber Sagnac interferometer as a parametric amplifier. The amplifier, which consists primarily of dispersion-shifted fiber that has zero dispersion at 1538 nm, is synchronously pumped with 7.7-ps pulses at 1539 nm. The wide bandwidth of the parametric gain permits tuning of the output signal pulses over a 40-nm range centered on the pump wavelength. The Sagnac interferometer decouples the pump wave from the oscillator cavity while a bandpass filter in the cavity transmits only the signal wave, thereby creating a singly resonant parametric oscillator that is phase insensitive. Whereas we demonstrate tuning over almost the entire bandwidth of Er-doped-fiber amplifiers, one could construct a similar device that operates near the 1310-nm zero-dispersion wavelength of standard telecommunication fiber.     

Synchronously pumped CdSe optical parametric oscillator in the 9-10 microm region

Continuous mode-locked operation of a singly resonant, synchronously pumped optical parametric oscillator (SPOPO) based on CdSe has produced idler output tuned over the range of 9.1-9.7 microm, the longest wavelength generated so far to our knowledge from a SPOPO. Average idler powers as high as approximately 70 mW are generated in the crystal. Tandem pumping with a diffraction-grating-tuned parametric oscillator in periodically poled lithium niobate provides a convenient and agile means of tuning the noncritically phase-matched CdSe device. The absence of any detrimental thermal effects in the CdSe crystal suggests that significant further power scaling should be possible, with idler tuning ranges extendable to cover 8-12 microm.     

High-repetition-rate ultrashort-pulse optical parametric oscillator continuously tunable from 2.8 to 6.8 mum

We describe a synchronously pumped femtosecond optical parametric oscillator based on periodically poled LiNbO(3) that is broadly tunable in the mid infrared. A transmission window of periodically poled lithium niobate beyond the conventionally accepted infrared absorption edge of 5.4 mum has been exploited to produce idler pulses that are tunable across a wavelength range of 4 mum , with milliwatt-level output powers at wavelengths as long as 6.8 mum . We also present experimental tuning results that are in good agreement with the theoretical phase matching predicted from published infrared-corrected Sellmeier equations for LiNbO(3) .     

Picosecond synchronously pumped optical parametric oscillator delivering transform-limited pulses in the degeneracy region

We report about a PPKTP optical parametric oscillator synchronously pumped by a picosecond Ti:Sapphire laser. The system is tunable in the spectral region around 1.55 μm which corresponds to the degeneracy wavelength. Nevertheless, it is able to deliver transform-limited pulses thanks to the insertion of a properly designed birefringent filter which ensures single-frequency operation as well. The resonating wavelength can be tuned for more than 100 nm by a simple rotation of the filter and is proven to be insensitive to cavity length detuning and pump wavelength drift.     

Femtosecond optical parametric oscillator based on periodically poled KTiOPO(4)

We report a femtosecond optical parametric oscillator based on a periodically poled KTiOPO(4) crystal for which quasi-phase matching is achieved with a 24-microm poling period. The singly resonant parametric oscillator, synchronously pumped by a Ti:sapphire laser at a wavelength of 758 nm, generates a signal at 1200 nm and an idler at 2060 nm. The maximum signal power conversion efficiency of the device is 22% with a pump depletion of 69%. We tune the signal wavelength over a 200-nm band by changing the cavity length. In addition, pump wavelength tuning provides output tunability in the 1000-1235-nm range.     

Experimental investigation and numerical simulation of the influence of resonator-length detuning on the output power,pulse duration and spectral width of a cw mode-locked picosecond optical parametric oscillator

We report on a cw mode-locked non-critically phase matched KTP optical parametric oscillator synchronously pumped by a picosecond Ti:Sapphire laser. High average signal output power of up to 950 mW over a large tuning range has been achieved. For this OPO the influence of resonator-length detuning on the output power, pulse duration and spectral bandwidth has been investigated. The measured data are in good agreement with the results of a numerical simulation using a split-step Fourier method which considers the group-velocity mismatch, the group-velocity dispersion and the self-phase modulation. The numerical simulation also describes the measured strong pump depletion and its influence on the OPO output and efficiency.     

BiB3O6 femtosecond optical parametric oscillator

We report a femtosecond optical parametric oscillator (OPO) based on the nonlinear material BiB3O6. The OPO is synchronously pumped in the blue by the second harmonic of a Kerr-lens-mode-locked Ti:sapphire laser. It can provide wide and continuous tuning across the entire green-yellow-orange-red spectral range with a single crystal and a single set of mirrors. Using a 500 microm BiB3O6 crystal and collinear type I (e+e->o) phase matching in the optical yz plane, a signal wavelength range of 480-710 nm is demonstrated with angle tuning at room temperature at average output powers of 270 mW. With 220 fs blue pump pulses, near-transform-limited signal pulses of 120 fs duration have been obtained at 76 MHz repetition rate.     

Dual‐wavelength optical parametric oscillator using antiresonant ring interferometer

A novel technique for coupling of two resonant optical cavities using an antiresonant ring (ARR) interferometer is reported. By deploying two synchronously‐pumped femtosecond optical parametric oscillators (OPOs), it is shown that the use of an ARR can provide an intracavity common path for the two oscillating fields, but without gain coupling between the two nonlinear media. The new technique permits the generation of two signal (idler) wavelengths, which can be independently and arbitrarily varied across the OPO tuning range. The absence of gain coupling also enables unrestricted and uninterrupted tuning through wavelength degeneracy at any arbitrary point within the OPO tuning range. It is shown that signal wavelength pairs tunable across 1500–1580 nm, corresponding to a frequency separation from ∼ 10 THz down to exact degeneracy, can be generated from the coupled OPOs, limited only by the reflectivity of the available mirrors.     

2.5-GHz repetition-rate singly resonant optical parametric oscillator synchronously pumped by a mode-locked diode oscillator amplifier system

We report on an optical parametric oscillator (OPO) that is synchronously pumped directly by a diode laser. This laser is an actively mode-locked master-oscillator power-amplifier system that produces 20-ps pulses at 927 nm with a repetition rate of 2.5 GHz and an average power of 0.9 W. The OPO, which is a singly resonant device based on periodically poled lithium niobate, generates 7.8-ps pulses. The OPO threshold is 300 mW of average pump power, and the maximum average idler output power is 78 mW at a wavelength of 2100 nm. By changing the crystal temperature we can wavelength tune the output in the ranges 1530-1737 nm (signal) and 1986-2348 nm (idler). Rapid wavelength tuning of the OPO over 46 nm (signal) and 74 nm (idler) is achieved through tuning the cavity length over 28 microm by use of a piezoelectric transducer.     

飞秒脉冲正交位相压缩光的产生

利用锁模飞秒脉冲激光二次谐波为抽运源, 同步抽运单共振光学参量振荡器, 抽运光中心波长为425 nm, 重复率为76 MHz, 脉宽180 fs, 光学振荡器下转换晶体采用Ⅰ类共线PPKTP, 实验上实现了压缩度为2.58 dB的正交位相压缩光.考虑到实验系统的效率, 可以推知光学参量振荡器输出的下转换光压缩度为 4.48 dB. 关键词： 同步抽运光学参量振荡器 压缩光 锁模飞秒脉冲     

Rapid infrared wavelength access with a picosecond PPLN OPO synchronously pumped by a mode-locked diode laser

We theoretically and experimentally investigate wavelength tuning of synchronously pumped optical parametric oscillators (OPOs) on changing the cavity length or the pump-repetition rate. Conditions for rapid and wide-range wavelength access are derived. Using an OPO pumped directly by a mode-locked diode-laser master-oscillator power-amplifier (MOPA) system, an all-electronically controlled access to near- and mid-infrared wavelengths is demonstrated. The singly (signal) resonant OPO is based on periodically poled lithium niobate (PPLN) and emits 8 ps idler pulses at a repetition rate of 2.5 GHz in the wavelength range 1986 to 2348 nm (signal: 1530 to 1737 nm). Wavelength tuning over 114 nm (signal) and 189 nm (idler) is achieved solely by electronically varying the repetition rate of the diode-laser oscillator over 720 kHz. By controlling the repetition rate with a programmable driver, an arbitrary emission sequence of the OPO on two wavelength channels is generated, with access times as short as 10 μs. 11 OPO wavelengths equally spaced in the range 1627–1689 nm (signal) or 2054–2154 nm (idler) could be addressed. Received: 6 September 2000 / Revised version: 16 March 2001 / Published online: 23 May 2001     

板条放大器同步泵浦的宽调谐MgO:PPLN中红外光参量振荡器（英）

搭建了Nd:YVO4/SESAM锁模激光器,采用LDA泵浦的Innoslab对其进行功率放大,最后同步泵浦MgO:PPLN实现了宽调谐皮秒中红外光参量运转。通过改变MgO:PPLN的温度和通道,实现了信号光1415~1557 nm、闲频光3362~4290 nm范围的宽调谐输出,其中最高的光光转换效率为17.5%。同步泵浦功率为16 W,脉冲重复频率为116.9 MHz时,同时获得1.33 W的1518 nm信号光和1.26 W的3558 nm闲频光输出。     

Synchronously pumped femtosecond optical parametric oscillator at 1053 nm

A femtosecond optical parametric oscillator synchronously pumped by a Ti:Sapphire oscillator is reported. By the cavity length tuning, the signal wavelength is continuously tuned from 1000 to 1200 nm. The average output power of 32 mW is obtained at 1053 nm. The pulse width is measured to be 342 fs by intensity autocorrelation method. In addition, we observed bichromatic emission during the cavity length tuning process. Supported by the National High Technology Program Research and Development Program of China, the National Natural Science Foundation of China (Grant Nos. 60490280 and 10804128), and the National Basic Research Program of China (Grant No. 2007CB815104)     

同步泵浦腔内倍频飞秒KTP光参量振荡器

采用光谱物理公司生产的，平均输出工为１．１Ｗ，脉宽为９０ｆｓ的再生锁模掺钛蓝宝石（Ｔｉ：Ｓａｐｐｈｉｒｅ）激光器作为泵浦源，ＫＴＰ作为非线性光学介质，以及ＢＢＯ作为腔内倍频晶体，制成了一台同上泵浦腔内倍频飞秒ＫＴＰ光学参量振荡器，其输出调谐范围５２８ｎｍ至５８６ｎｍ，最佳平均输出功率为２４０ｍＷ左右，脉宽约为１００ｆｓ。在无反馈伺服系统的情况下，该参量振荡器可维持振荡达三个小时。     

Amplitude and phase measurement of mid-infrared femtosecond pulses by using cross-correlation frequency-resolved optical gating

We describe a cross-correlation-based frequency-resolved optical gating (XFROG) technique for simultaneously measuring the amplitude and phase of two ultrashort pulses that have different wavelengths but are derived from a common mode-locked oscillator. A measurement is presented in which 4.0-mum mid-IR pulses from a synchronously pumped femtosecond optical parametric oscillator (OPO) are characterized by mixing with the 770-nm OPO pump pulses. Details of the pulse-retrieval algorithm are included, together with examples of pulse data retrieved from the experimentally measured XFROG trace.     

LiNbO3电光调谐光学参变振荡器

在光学参变振荡器中 ,角度或温度调谐方式的最大缺陷就是参变光波长变化较慢 ,调谐操作复杂 ;电光调谐方式具有调谐速度快 ,操作简单的优点。利用非线性光学晶体LiNbO3 的电光效应 ,在 1 0 6 4 μmNd∶YAG激光器输出的抽运光作用下 ,切割角θ =4 7.5°,在垂直于 1.0 6 μm抽运光偏振方向上加 - 4 .5 +4.5kV直流电压 ,实现参变光波长调谐输出 ,输出光能量约为 2 6mJ左右 ,转换效率 η≈ 17.3%。实验所得的参变光波长变化与调谐电压的线性关系与理论计算相吻合 ,为实现光学参变振荡器的快速调谐快速输出提供了一种可行的技术途径。     

Quadrature squeezing in an isolated pulse of light

Quantum properties of pulsed radiation obtained by cutting out a part of the signal from steady-state squeezed-light sources are investigated. The considered sources include a degenerate optical parametric oscillator, a sub-Poissonian injection-locked laser, and a synchronously pumped femtosecond optical parametric oscillator. Based on the statistical properties of steady-state radiation from these sources, we analyzed to what extent preservation of these properties is sensitive to the observation time.     

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.