Time-interval analysis of laser-pulse-timing fluctuations

A new technique has been proposed and demonstrated for measuring the pulse-timing fluctuations of mode-locked lasers at low Fourier frequencies. The time interval between the laser pulses is precisely measured by use of zero-dead-time counters referenced to a stable atomic oscillator. By combination of this method with the time-domain demodulation technique, the phase-noise power spectral density of a mode-locked Cr:LiSAF laser has been estimated for the 1-mHz-1-MHz Fourier frequency range, with a 240-dB dynamic range.     

Wideband phase-noise measurement of mode-locked laser pulses by a demodulation technique

A new method is proposed and demonstrated for measuring the phase noise (pulse timing fluctuations) of mode-locked lasers. The instantaneous phases of the pulse intensity are extracted in a time domain, and the phase-noise power spectral density is calculated from the demodulated signals. Compared with the conventional method based on the single-sideband phase-noise measurement, the proposed method has a larger dynamic range and a wider frequency span. The phase noise of a mode-locked Cr:LiSAF laser is measured for 50-mHz-1-MHz Fourier frequencies.     

Timing-jitter reduction of a mode-locked Cr:LiSAF laser by simultaneous control of cavity length and pump power

The pulse-repetition frequency of a mode-locked Cr:LiSAF laser has been stabilized to an electrical reference signal by simultaneous control of the laser cavity length and the pump power. The phase difference between the laser pulse and an electrical reference signal is detected by use of a digital phase detector and fed back to a piezoelectric transducer and to a laser diode injection current. A rms timing jitter of 7.5 fs relative to the reference was obtained for the 25-mHz-10-kHz bandwidth.     

Correlation between amplitude and phase noise in a mode-locked Cr:LiSAF laser

The coherence function between the amplitude and phase fluctuations of a mode-locked Cr:LiSAF laser has been measured with a time-domain demodulation technique. A relatively large correlation has been found for the noise components that originate in the pump-power fluctuation. Through an examination of the modulation-induced change in the noise power spectral densities, the influences of pump-power and cavity-length variations on these fluctuations have been investigated.     

Broadly tunable femtosecond Cr:LiSAF laser

We demonstrate wavelength tunability of femtosecond pulses over a range of more than 50 nm from a diode-pumped Cr:LiSAF laser. The mode-locking mechanism can be explained by soliton mode locking that is started and stabilized by a broadband semiconductor saturable-absorber mirror designed for low loss over the full reflection bandwidth of the underlying Bragg mirrors, which ultimately limits tunability. We obtain 45-fs pulses at 105-mW average output power and a maximum mode-locked average output power of 125 mW with 60-fs pulses.     

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.     

30 W Cr:LiSrAlF 6 flashlamp-pumped pulsed laser

We report the performance of a flashlamp-pumped Cr:LiSrAlF(6) (Cr:LiSAF) laser developed and built by us. The pumping cavity incorporates filters that select the flashlamps' emission spectrum to match the absorption bands of the gain medium, allowing control of the amount of nonradiactive decay heat contribution of the optical cycle, minimizing thermal effects on the laser operation. The laser generated 2 J pulses at 15 Hz, resulting in 30 W of average power, the highest power extracted from a Cr:LiSAF rod laser to our knowledge. We were able to conclude that the laser efficiency is affected by resonator configuration changes due to thermal lens effects, and not to thermal quenching of the Cr:LiSAF luminescence.     

自锁模Cr:LiSAF激光器的特性研究

本文分析上转换过程及荧光热猝灭效应对Cr:LiSAF激光器的泵浦阈值和输出功率的影响,由此得出Cr:LiSAF激光器特别适合低功率泵浦.分析了三镜腔结构的特性,选择了腔的较佳参数,实现了在750mW的氩离子激光泵浦下三镜腔Cr:LiSAF激光器的自锁模运转.     

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.     

高效率连续激光二极管泵浦Cr:LiSAF激光器

报道了500mW激光二极管端面泵浦Cr:LiSAF激光器连续运转的实验研究结果.特别是在分析了泵浦光与腔模的耦合情况后,提出了一套与泵浦源相适应的准直聚焦系统,提高了耦合效率.实验对两种不同掺杂浓度和不同形状的Cr:LiSAF晶体进行了研究,在850nm的中心波长处获得最大输出功率分别为20mW和13mW,斜效率分别为10.3%和7.8%,并对实验结果作了讨论.     

未来激光探潜和对潜通信技术的发展

潜艇是现代军事力量的重要组成部分 ,对潜通信及潜艇探测是世界各军事强国正在研究的一个重要的 ,但又未完全解决的问题。在光源方面 ,美国的该项研究经历了倍频Nd∶YAG激光器、XeCL和HgBr喇曼频移激光器阶段 ,目前正在进行LD泵浦LiSAF类激光器的研究 ,中国的此项研究还停留在闪光灯泵浦的倍频Nd∶YAG激光器阶段。 90年代出现的Cr3 +∶LiSAF激光器及其倍频“海军蓝”激光极有希望成为新一代水下应用激光器 ,其 45 7 5nm波长是水下应用的最佳波长。经过改进的Cr3 +∶LiSGaF晶体更是保持了Cr3 +∶LiSAF的优点 ,克服了其热特性差的缺点。Cr3 +∶LiS GaF的另一个优点是可以用红光LD泵浦 ,可制成全固态高效紧凑的激光系统 ,易于达到军用要求     

宽谱可调谐的全固化Cr:LiSAF激光器

报道了调谐范围达130nm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32.8mW。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783~913nm连续可调谐输出,在840nm处获得115mW的最大输出功率,在800~900nm的区间内,输出功率超过80mW。用棱镜作为调谐元件,调谐范围达802~887nm,最大输出功率为6.5mW。从调谐范围和输出功率看,BF的调谐效果更好。     

14-fs pulse generation in Kerr-lens mode-locked prismless Cr:LiSGaF and Cr:LiSAF lasers: observation of pulse self-frequency shift

Kerr-lens mode-locked Kr-laser-pumped Cr:LiSGaF and Cr:LiSAF lasers containing only two newly developed low-loss chirped mirrors instead of conventional dielectric resonator mirrors and generating pulses of widths as small as 14-fs with as much as 100 mW of average output power are reported. We report what is to our knowledge the first experimental observation of a pulse self-frequency shift in crystalline active media that are characteristic of such short pulses at megawatt intracavity peak powers. We also believe this phenomenon to be one of the significant limiting factors for pulse duration in femtosecond Cr:LiSAF-type lasers.     

半导体激光器泵浦的Cr:LiSAF激光器

本文报道了用半导体激光器泵浦Cr:LiSAF激光器腔的设计以及输出特性,在用准连续波泵浦时,阈值平均功率为42mW,在泵浦平均功率为60mW时得到了3mW的激光输出.     

纵向抽运Cr3+∶LiSAF6激光器小信号增益的理论研究

提出了计算小信号增益的理论模型 ,用来研究纵向Cr3+∶LiSAF6激光器中抽运聚焦特性对小信号增益的影响。对Cr3+∶LiSAF6晶体小信号增益进行了最佳化计算 ,求出了几种给定抽运功率下腰斑半径和焦点位置的最佳值。计算结果表明 ,在最佳化条件下Cr3 +∶LiSAF6晶体小信号增益特性能够获得极大地改善     

Operative Characteristics of the Dual-wavelength Cr: LiSAF Laser

ＯｐｅｒａｔｉｖｅＣｈａｒａｃｔｅｒｉｓｔｉｃｓｏｆｔｈｅＤｕａｌ┐ｗａｖｅｌｅｎｇｔｈＣｒＬｉＳＡＦＬａｓｅｒＬＩＵＧｕｏｒｏｎｇＷＡＮＧＮｕｏＦＥＮＧＸｕａｎｑｉ（ＰｈｙｓｉｃｓＤｅｐａｒｔｍｅｎｔ，ＮｏｒｔｈｗｅｓｔＵｎｉｖｅｒｓｉｔｙ，Ｘｉ?..     

微型Cr:LiSAF激光器中泵浦光与输出光光斑形状的测量

本文从实验上对微型Cr:LiSAF激光器中泵浦光与输出光光斑进行了测量.     

半导体激光器纵向泵浦准连续Cr:LiSAF激光器的实验研究

用波长为653.2nm的半导体激光器实现了纵向泵浦Cr:LiSAF激光器的准连续运转,晶体平均吸收功率为140mW时获得激光输出,在LD最大输出功率范围内,晶体平均吸收功率为680mW时,可获得最大平均输出功率32mW,斜效率5.6%.     

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.     

自锁模Cr：LiSAF激光器的实验研究

以功率为９００ｍＷ，波长为４８８ｎｍ的单线氩离子激光作为泵浦源，在腔内不加任何主动调制器和可饱和吸收体的情况下实现了Ｃｒ：ＬｉＳＡＦ激光器的飞秒级自锁模运转，得到了脉冲宽度为４０ｆｓ，重复频率为１００ＭＨｚ，平均输出功率为４５ｍＷ的稳定的锁模脉冲序列。