Dual-wavelength synchronously mode-locked Nd:CNGG laser

We have experimentally demonstrated a dual-wavelength synchronously mode-locked Nd:CNGG laser based on the semiconductor saturable absorber mirror technique. Mode locking was achieved simultaneously on two gain bands of the crystal that have a central wavelength separation of 2.4 nm. The fundamental mode-locked pulse train has a repetition rate of 88 MHz and pulse duration of 5 ps, with an average output power of approximately 90 mW. Autocorrelation measurements show that each of the synchronously mode-locked pulses consists of a train of quasi-periodic beat pulses with a 660 fs pulse width and a 0.63 THz repetition rate.     

Dual-wavelength laser emission from an organic microcavity with terahertz beating

We report on the dynamics of laser emission from an anisotropic organic microcavity filled with the guest-host composite of tris-(8-hydroxy quinoline) aluminium (Alq₃) and 4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM). In a single microcavity, a linesplitting of 0.18 THz between two perpendicularly polarized laser modes is observed. We ascribe this effect to an optical anisotropy in the distributed Bragg reflectors surrounding the organic layer. The temporal behavior of the electromagnetic field is studied by an up-conversion technique and shows an optical beating of 0.18 THz. Two modeling approaches are used to gain insight in the temporal evolution and phase behavior of the two modes. Both point towards the presence of a phase-coupling mechanism in this system. PACS 42.55.Sa     

Difference frequency generation with a synchronously mode-locked cw dye laser system

The generation of continuous trains of tunable infra-red pulses by the nonlinear mixing of the wave-lengths available from a self-contained synchronously mode-locked cw dye laser is described. The factors determining the optimization of the process are identified and their roles demonstrated.     

Formation of synchronously mode-locked dye laser pulses

The generation process of synchronously mode-locked dye laser pulses within a linear cavity configuration containing a dye as an active medium and a bandwidth-limiting element is treated. The initial build-up of pulses from the noise as well as the steady-state regime are discussed. The circulation of the pulse in the cavity is described by a nonlinear integral equation. A computer analysis provides statements concerning the speed and the stages of the initial build-up. Furthermore it allows the discussion of steady-state regimes with good mode-locking as well as regimes outside of this region, for instance double and multiple pulse regimes or non-steady-state regimes.     

Study of synchronously mode-locked and internally frequency-doubledcw dye laser

The analysis of the characteristics of a synchronously mode-locked and internally frequency-doubled dye laser is presented. Dependence of dye laser pulse characteristics on the cavity length mismatch of the pump laser and dye laser is studied. Variation of the minimum pulsewidth with intracavity bandwidth and the harmonic conversion efficiency is presented in the form of graphs.     

基于石墨烯可饱和吸收体的纳秒锁模掺铥光纤激光器

报道了一种基于石墨烯可饱和吸收体的纳秒锁模掺铥光纤激光器.该激光器采用环形腔结构,利用自制的三层石墨烯薄膜作为可饱和吸收体实现锁模.同时在腔内插入一个窄带光纤光栅,约束腔内起振的纵模数,适当调节抽运功率和偏振控制器的角度,得到了重复频率为3.8 MHz、脉宽在3.8—94.3 ns之间灵活可调的2μm纳秒锁模脉冲输出,整个脉宽调节范围超过90 ns.此外,由于获得的兆赫兹纳秒锁模脉冲时间带宽积在49—1119范围内,即存在强烈的啁啾,因而可作为2μm波段啁啾脉冲放大系统中的种子源使用.     

Cavity detuning effects in the synchronously mode-locked CW dye laser

A detailed numerical model analysis of the synchronously mode-locked CW dye laser is presented. In the analysis, good mode-locking is found mainly for negative cavity detuning. The calculated cavity length detunig effects are compared with the results of experiments performed on the Oxazine-1 dye laser. The agreement between theory and experiment is satisfactory. The experimental good mode-locking regime is predicted correctly by this analysis. The present calculations are also compared with the hitherto reported qualitative model analyses with a gaussian dye pulse approximation. The validity of these model analyses is examined.     

Frequency offset locking of a synchronously pumped mode-locked dye laser

We have developed a scheme of frequency offset locking for transferring the frequency stability of a commercial dye laser to a synchronously pumped mode-locked dye laser. By observing the beat frequency between the two dye lasers, mode stability of less than 2 MHz has been observed for the mode-locked dye laser mode. The use of the mode-locked system as a spectroscopic tool has been demonstrated by observing Doppler-free multiple pulse two photon spectra of the sodium 3S-4D transition.     

Bistable operation of a dual-wavelength synchronously mode-locked cw dye laser

Bistable operation of a dual-wavelength synchronously mode-locked cw dye laser is reported. Wavelength switching is found to depend on the pump power and the dye laser cavity lengths.     

Near-infrared subpicosecond pulse generation in a synchronously mode-locked cw dye laser

Tunable subpicosecond pulses have been obtained from a synchronously mode-locked Oxazine-1 dye laser by tandem pumping with output pulses of a mode-locked Rhodamine 6G dye laser. The effects of cavity detuning on the pulse-width and the second harmonic power (the peak intensity of the autocorrelation trace) have been investigated. The experimental results are found to be in good agreement with those predicted by a recent model analysis.     

Timing and detuning studies of a synchronously pumped mode-locked dye laser

The timing relationship between a synchronously pumped mode-locked dye laser and its pump laser is explored experimentally and theoretically. The experimental data is in quantitative agreement with numerical solutions of a semiclassical model that includes no free parameters. The data also agrees qualitatively with an approximate, analytic distillation of this model which is presented here for the first time. Our study has a direct bearing on the jitter and the long term stability of these important ultrashort pulse lasers.     

On noise and fluctuations in a synchronously mode-locked cw laser system

A single-shot and synchronously-scanned streak camera, autocorrelation and noise spectrum analysing techniques are utilized to study the output characteristics of synchronously mode-locked cw lasers. Four main conclusions are drawn: (i) the pulse train from a synchronously-pumped dye laser reveals, besides phase jitter, considerable pulse shape fluctuations; (ii) autocorrelation measurements may be highly misleading when actual pulse shapes are considered; (iii) both the phase jitter and pulse shape fluctuations of the dye laser output are caused by the phase fluctuations of the pumping ion laser pulse train; (iv) the phase jitter of the ion laser proceeds from the fluctuations in the cavity roundtrip time with a characteristic time of about 5 s. Under optimum conditions the rms noise of the dye laser output was 2% and the phase jitter with respect to the rf sine drive of the acousto-optical mode-locker, 30 ps. A qualitative explanation fo the noise properties is given.     

基于增益光纤长度优化的双波长运转掺铒光纤锁模激光器

构建了可自启动的双波长运转掺铒光纤锁模激光器.通过优化增益光纤长度,利用掺铒光纤在1530nm附近的再吸收效应调节激光器的增益谱,使激光器在1530nm和1560nm附近具有相同的增益强度.实验中采用31cm掺铒光纤作为增益光纤,以透射式半导体可饱和吸收体作为锁模器件,实现了自启动双波长锁模运转.激光器锁模输出重复频率为58.01MHz,信噪比为58.2dB,最高输出功率为4.8mW.锁模输出的光谱在1532.4nm和1552.3nm处具有两个强度接近的谱峰,谱峰间距约为20nm.该激光器无需手动调节即可实现双波长运转,更便于实际使用.     

Dual-wavelength passively mode-locked Nd: GdVO4?laser?with?orthogonal polarizations

A passively mode-locked dual-wavelength Nd: GdVO₄ laser with orthogonal polarizations is experimentally demonstrated. By changing the absorbed pump power, the laser can mode lock either at 1063?nm (with ?? polarization) or 1065 nm (with ?? polarization), or simultaneously at both wavelengths with orthogonal polarizations. When mode locked at 1063 nm and 1065?nm, the laser produced pulses of 10?ps and 5.9?ps, respectively, with repetition rates of 143.7?MHz and 143.9?MHz. When simultaneously mode locked at both wavelengths, the pulsewidth was about?7?ps. The laser was demonstrated by exploiting the thermal lens and birefringence of the Nd: GdVO₄ crystal. The laser uses one cavity and does not require the insertion of additional optical components.     

Stable noise-like pulse generation in all-PM mode-locked Tm-doped fiber laser based on NOLM

A stable noise-like(NL) mode-locked Tm-doped fiber laser(TDFL) relying on a nonlinear optical loop mirror(NOLM) was experimentally presented. Different from the previous NL mode-locked TDFL with NOLM, the entire polarizationmaintaining(PM) fiber construction was utilized in our laser cavity, which makes the oscillator have a better resistance to environmental perturbations. The robust TDFL can deliver stable bound-state NL pulses with a pulse envelope tunable from～14.1 ns to～23.6 ns and maximum pulse energy of ～40.3 n J at a repetition rate of ～980.6 k Hz. Meanwhile, the all-PM fiber laser shows good power stability(less than ～0.7%) and repeatability.     

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     

Pulse dynamics controlled by saturable absorber in a dispersion-managed normal dispersion Tm-doped mode-locked fiber laser

Based on the coupled Ginzburg-Landu equation,we numerically investigate the pulse dynamics in a dispersion-managed normal dispersion Tm-doped mode-locked fiber laser.The influences of the modulation depth and saturation power of saturable absorber on the pulse dynamics are presented.The simulation results show that these parameters are crucial to achieve high pulse energy and high pulse peak power pulsed laser near 2-μm wavelength.     

Wideband frequency modulation of a mode-locked fiber laser

We have demonstrated wideband frequency modulation of the frequency comb lines of a high-repetition-rate fiber laser. With a modulation frequency of only approximately 10 kHz, we have generated modulation indices in excess of 250. Although internally modulated, the laser remains stable with 2-kHz linewidths, and thus the 10-kHz modulation sidebands are still clearly resolved even after propagation over several hundred kilometers. This unique characteristic is used for simultaneous measurement of propagation distances to 1-m resolution and velocities of less than 3 mm/s over a distance of greater than 50 km.     

Generation of synchronised ultrashort pulses using a dual wavelength synchronously mode-locked CW dye laser

The properties of a dual wavelength synchronously mode-locked cw dye laser are described. Results are presented which show that good mode-locking is obtainable under dual wavelength conditions. Cross-correlation measurements indicate that the time separation of the pulses depends on gain saturation within the dye.