Broadly tunable femtosecond solid-state laser sources

The techniques of coupled-cavity modelocking and self-modelocking in which intensity-induced nonlinear effects are exploited have been reviewed for broad-band gain media. Particular emphases have been placed upon the archetypical colour-centre and titanium-sapphire laser configurations in which these techniques were first demonstrated and subsequent refinements are set in context. A femtosecond optical parametric oscillator pumped by a self-mode-locked titanium-sapphire laser has also been described as an exemplar of a practical means of extending the source tunability into the mid-infrared spectral region.     

宽谱可调谐的全固化Cr:LiSAF激光器

报道了调谐范围达130 nm的的V型腔端面泵浦全固化Cr:LiSAF激光器。研究了V型腔结构的重要参数,优化了腔型设计以提高激光器的效率。激光器自由运转输出时,斜效率最高达39.2%,泵浦阈值最低为32.8 mW。对比分析了双折射滤光片(BF)和棱镜的调谐效果。在腔内插入BF调谐,实现了783~913 nm连续可调谐输出,在840 nm处获得115 mW的最大输出功率,在800~900 nm的区间内,输出功率超过80 mW。用棱镜作为调谐元件,调谐范围达802~887 nm,最大输出功率为6.5 mW。从调谐范围和输出功率看,BF的调谐效果更好。     

Diode-pumped tunable laser with dual Cr：LiSAF rods

We propose and demonstrate a simple approach to lower the thermal quenching effect and improve the output power of Cr:LiSAF lasers, which is accomplished by employing two laser rods. The resonator contains two laser rods and is designed by using two ``X' folding cavities in cascade. A tunable laser output of $\sim $ 180\,mW has been achieved with the pump of single-striped laser diodes. Compared with lasers using single gain rod, the laser with dual rods shows less severe thermal effect and increases the output by more than two times.     

Broadly tunable continuous-wave diode-pumped Cr4+:YAG laser

We describe a widely tunable, continuous-wave, room temperature Cr⁴⁺:YAG laser with direct pumping by two high brightness 4 W InGaAs laser diodes. In a tunable configuration, the output wavelength covered a span of 197 nm (1356–1553 nm) and provided a maximum power of 195 mW. A maximum non-tunable output power of 260 mW was obtained with a 0.6% transmission output coupler (OC) and 6.6 W of incident pump power. Pumping at two different wavelengths, 911 and 968 nm, was investigated.     

High-average-power diode-pumped femtosecond Cr:LiSAF lasers

Received: 27 February 1997/Revised version: 14 April 1997     

Broadly tunable compact continuous-wave Cr(2+):ZnS laser

We report the development of a continuous-wave, room-temperature Cr(2+) ZnS laser that is compact and tunable over 700 nm. The laser is pumped by a diode-pumped Er-fiber laser and generates 0.7 W of linearly polarized radiation at 2.35microm , at up to 40% slope efficiency. Cr(2+) ZnS directly diode-pumped at 1.6microm yields polarized radiation that is tunable over 400 nm at up to 25 mW of output power. A comparison of Cr(2+) ZnS with Cr ZnSe (70 mW, 350 nm) in a similar setup is given. As opposed to Cr ZnSe, the Cr ZnS laser is intrinsically polarized. Finally, we observe sensitization of the output radiation by a few milliwatts of the visible (470-500-nm) and near-infrared (740-770-nm) radiation.     

Pulse duration limitations in a diode-pumped femtosecond Kerr-lens mode-locked Cr:LiSAF laser

Received: 20 February 1997/Revised version: 24 April 1997     

All-solid-state diode-pumped Cr:LiSAF femtosecond oscillator and regenerative amplifier

3+ :LiSrAlF₆ (Cr:LiSAF) regenerative amplifier, seeded by a diode-pumped Cr:LiSAF femtosecond oscillator. The amplifier produced pulses of less than 200 fs duration and greater than 1 μJ energy at repetition rates of up to 25 kHz. Received: 27 February 1997/Revised version: 16 April 1997     

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.     

Pulse timing stabilization of a mode-locked Cr:LiSAF laser

The pulse repetition frequency of a mode-locked Cr:LiSAF laser has been stabilized to an electrical reference oscillator by use of an electrical feedback technique. The phase and frequency differences between the laser and the reference are detected by use of a digital phase detector, which overcomes the difficulties of a conventional double-balanced mixer. We obtained rms timing jitters of 20 fs (25 mHz-10 kHz) and 7 fs (25 mHz-1 kHz) relative to the reference.     

High-order dispersion-resulted tunable multiwavelength femtosecond laser

Resonant dispersive waves generated by high-order dispersion in a Ti:sapphire mode-locked solitary laser are investigated and experiments are found to be in good agreement with theoretical analysis. Both theory and experiment show that the wavelength differences can be tuned in a large range via changing the cavity dispersion. This simple technique can be applied to the fields where tunable femtosecond pulses at multiple wavelengths are needed. The described mechanism may be applied in other systems where solitons are known to exist.     

High-peak-power femtosecond Cr:forsterite laser system

Received: 25 June 1998     

White-light frequency comb generation with a diode-pumped Cr:LiSAF laser

We have created a broad spectrum spanning more than an optical octave by launching femtosecond pulses from a battery operated Cr:LiSAF laser into a photonic crystal fiber. Despite the massive broadening in the fiber, the comb structure of the spectrum is preserved, and this frequency comb is perfectly suited for applications in optical frequency metrology.     

Broadly tunable mid-infrared femtosecond optical parametric oscillator using all-solid-state-pumped periodically poled lithium niobate

We describe a high-repetition-rate femtosecond optical parametric oscillator (OPO) that was broadly tunable in the mid infrared. The all-solid-state-pumped OPO was based on quasi-phase matching in periodically poled lithium niobate. The idler was tunable from approximately 1.7 mum to beyond 5.4 mum, with maximum average power levels greater than 200 mW and more than 20 mW of average power at 5.4 mum. We used interferometric autocorrelation to characterize the mid-infrared idler pulses, which typically had durations of 125 fs. This OPO had a pumping threshold as low as 65 mW of average pump power, a maximum conversion efficiency of >35% into the near-infrared signal, a slope efficiency for the signal of approximately 60%, and a maximum pump depletion of more than 85%.     

Broadly tunable pulsed laser for the infrared using color centers

We report design criteria and performance characteristics of a pulsed color center laser, excited by a nitrogen-pumped dye laser. One hundred watts peak power with 2% energy conversion efficiency and a 0.03 cm^-1 bandwidth are obtained near 2.7 μm.     

Femtosecond single-mode diode-pumped Cr:LiSAF laser mode-locked with single-walled carbon nanotubes

A low threshold Cr:LiSAF laser pumped with an inexpensive single-mode laser diode emitting 120 mW was passively mode-locked with a novel ultrafast saturable absorber mirror based on single-walled carbon nanotubes (SWCNT-SAM). Pulses as short as 122 fs were achieved, tunable across 14 nm. A second pump diode coupled in polarization allowed to shorten the pulse duration to 106 fs, with up to 24-mW output power.     

Improvement of the operation parameters for a Cr:LiSAF ultrashort-pulsed laser

The optimization of the pumping power that is focused on a gain medium inside an optical cavity is fundamental for increasing the efficiency of the power transferred inside a crystal, in this way increasing the output power of the laser. Nevertheless, in the case of pumping with a highly astigmatic laser diode, an undesirable form of the beam is focused on the cavity and the process to improve the cross section and sizes of the beam produce a notable reduction in the effective pump power ultimately focused in the crystal. The cavity design improvements for a Cr:LiSAF laser pumped with a 200 um × 1 um laser diode emission is presented for three different configurations, Z, V, and ring. The pump power is introduced in the cavity through a simple optical array, coupling more than 83% of the laser-diode power. The design requirements for the resonant cavity are reviewed in order to improve the coupling between the fundamental mode of the cavity and the cross-section form of the pumping beam. The stability limits of the cavities and Kerr sensitivity region are presented.     

Injection-seeded, gain-switched tunable Cr:ZnSe laser

We report a narrow-linewidth, tunable, gain-switched Cr:ZnSe laser operating between 2255 and 2455 nm. The spectral width of the laser was reduced from 125 nm to 0.3 nm by using injection seeding. Seeding was achieved with a second tunable CW Cr:ZnSe laser. The output wavelength was varied by tuning the wavelength of the seed laser. The seeded oscillator produced as high as 157 μJ pulses with 598 μJ incident pump pulse energy at a repetition rate of 1 kHz. The slope efficiency was determined to be 26%.     

Continuous-wave tunable Cr2+:ZnS laser

We report the first continuous-wave tunable over ∼280 nm around 2.3 μm room-temperature operation of a chemical vapor transport-grown and diffusion-doped Cr²⁺:ZnS laser, pumped by a Co:MgF₂ laser at 1.67 μm and generating over 100 mW of output power at 16% slope efficiency. The self-consistent results of the laser and spectroscopic analysis demonstrate a large potential of this crystal as an active medium for diode-pumped tunable mid-infrared sources. Received: 7 January 2002 / Revised: 14 March 2002 / Published online: 2 May 2002     

Frequency-dispersive method for improving broad-band SBS phase conjugation of Cr:LiSAF laser

After passing through four dispersive-prisms, the Q-switched Cr.LiSAF laser with broad frequency band is focused into carbon disulfide (CS2) to produce backward stimulated Brillouin scattering (SBS). Our experimental results and illustrative analysis have shown that this frequency-dispersive method can efficiently reduce the broad-band SBS intensity threshold, compress its pulsewidth, and improve the beam quality.