Travelling-wave operation of a tunable cw dye laser

A ring cavity configuration for a tunable cw dye laser is described. A substantial reduction of the output bandwidth of the ring laser with increase in power for unidirectional or traveling-wave operation has been demonstrated. The advantages of the ring configuration for single-frequency operation of cw dye lasers are explored.     

Multiple-Pulse Operation in Passively Mode-Locked Fibre Laser with Positive Dispersion Cavity

We report the observation of rectangular shape spectrum in passively mode-locked fibre laser with positive dispersion cavity. The spectrum is broad and flat, and 3dB bandwidth can be up to 17.61 nm. Multiple-pulse operation is observed in our laser system. The spectrum width, pulse energy, pulse width and peak power of the mode-locked laser output change with the appearance of multiple-pulse operation.     

微机械FP腔可调谐滤波器在WDM系统中的串扰分析

介绍了一种以FP谐振腔为基础,用于波分复用系统的MOEMS器件-电控可调谐FP光滤波器.器件采用微电子机械加工技术研制.研究了FP型解复用器在密集波分复用系统中引入的信道间串扰对系统的影响,并分别讨论了激光器线宽、滤波器带宽、信道间距对串扰的影响.在信道间隔为100GHz,激光器线宽为5GHz,串扰可达到-21dB左右.     

Spectral dynamics of an all solid-state frequency-shifted feedback laser

A frequency-shifted feedback (FSF) laser has multi frequency components with simultaneous linear chirping in its oscillation spectrum even though the gain medium is homogeneously broadened. The spectral intensity and its bandwidth were analyzed by the proposed spectral dynamics model based on the regenerative amplification of the continuously chirped comb components with phase shift according to each round trip in the cavity. The spectral intensity peaks at an instantaneous frequency which depends on the net gain in the cavity and the gain bandwidth of atomic transition. The oscillation bandwidth is defined as the product of the saturation-broadened bandwidth and the total resonant modes contributing to the FSF operation.     

To narrow laser linewidth by utilizing dispersion characteristics of Gires-Tournois etalon

A longer laser resonator length is benefit for laser linewidth, but harmful for single-frequency operation. A novel way is suggested to narrow the bandwidth of a Fabry-Perot （FP） cavity through increasing the derivative of one round-trip phase shift with respect to the frequency. It can be implemented by replacing one of two FP mirrors with a Gires-Tournois etalon （GTE）, called FPCT, as a dispersion element. FPGT resonator has additional axial modes due to the GTE reflection phase shift. Theoretical analyses show that the bandwidth of additional axial modes can be 1% of that of a conventional FP cavity. A distributed feedback （DFB） laser diode can employ FPGT resonator to achieve ultra-narrow linewidth laser. It is shown that the effect of refractivity fluctuation in the gain medium on the linewidth is little, and kilohertz linewidth is achievable for such a device.     

Wideband and high frequency stabilization of an injection-locked Nd:YAG laser to a high-finesse Fabry Perot cavity

High frequency stabilization of a 2.2-W injection-locked laser-diode-pumped Nd:YAG laser to a high-finesse optical cavity has been realized by frequency control of the master laser. With the help of an external electro-optical modulator, the feedback bandwidth was extended to 1 MHz and the frequency noise relative to the reference cavity was suppressed to 3 x 10(-4) Hz/Hz(1/2) below 1 kHz. This feedback laser system is an ideal laser source for gravitational wave detectors, which require both ultralow frequency noise and high output power.     

Dye laser pumped, continuous-wave KTP optical parametric oscillators

4 (KTP) optical parametric oscillators (OPOs) with pump and idler resonant cavities. With a linear two-mirror cavity the pump power at threshold was 70 mW. The single-frequency signal and idler output wavelengths were tuned in the range of 1025 to 1040 nm and 1250 to 1380 nm by tuning the dye laser in the range of 565 to 588 nm. With a dual three-mirror cavity the threshold was 135 mW. Pumped by 500 mW of 578 nm radiation the 1040 nm single-frequency signal wave output power was 84 mW. Power and frequency stable operation with a spectral bandwidth of less than 9 MHz was obtained by piezo-electrically locking the length of the pump resonant cavity to the dye laser wavelength. Similar performance was achieved by placing the idler resonant OPO inside the resonator of the dye laser. With this system power stable and single-frequency operation was achieved with a spectral bandwidth of less than 11 MHz for the idler wave. Received: 3 February 1998/Revised version: 9 March 1998     

Dual-wavelength bandwidth-narrowed output of a high-power diode laser using a simple external cavity

Using an external cavity consisting of an etalon and a mirror, dual-wavelength operation of a high-power broad-area multi-stripe diode laser is achieved. The reflection of the etalon is used as the output beam of the system. The free-running bandwidth of the laser diode is about 2.0 nm. At dual-wavelength operation, the bandwidth of each wavelength component is narrowed to about 0.07 nm, while the space between them is 1.65 nm, determined by the FSR of the etalon. We obtain an available dual-wavelength output power of 2.0 W at the drive current of 6.5 A. The power ratio of the components at two different wavelengths can be changed by changing the temperature of the diode laser. To tune the wavelength of the dual-wavelength output, the temperature of the laser diode and the tilt angle of the etalon are changed simultaneously PACS 42.55.Px; 42.60.Fc; 42.60.Da     

Single mode operation of a narrow bandwidth dye laser using a single prism, grazing incidence grating long cavity

The single mode pulsed dye laser is an attractive tool for many spectroscopic applications. Long cavity tunable dye lasers generally operate in multi-longitudinal modes within the bandwidth of gain profile. Single longitudinal mode oscillation can be obtained by either making the cavity short enough or introducing an additional loss mechanism, in which all modes but one have a gain less than their loss. A new technique to achieve single mode operation in a long cavity dye laser, based on Rhodamine 6G dye in ethanol and ethylene glycol solution, pumped by a high repetition rate copper vapor laser, is reported. This laser, which operates in three modes in grazing incidence grating configuration (cavity length of 16 cm), has been made to lase in single mode by increasing the loss in the resonator through beam walk-off.     

A tunable,single mode,injection-locked flashlamp pumped dye laser

A tunable, very narrow bandwidth, flashpumped dye laser is described. Publse energies up to 50 mJ at a bandwidth of less than 30 MHz, and with a divergence of 0.4 mrad, are obtained. Spectral narrowing and tuning is achieved by injection locking of the pulsed laser to the radiation, of a tunable cw dye laser. The cavity is designed for single longitudinal and transverse mode operation, with a mode diameter large enough to fill the active medium. This work was supported in part by the Israel commission for Basic Research, and in part by a grant from the United States Israel Binational Science Foundation (BSF), Jerusalem, Israel.     

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.     

Efficient skew-angle cladding-pumped tunable narrow-linewidth Yb-doped fiber laser

A skew-angle cladding-pumped tunable Yb-doped fiber laser is presented. The laser was tunable over more than 30 nm, from 1022 to 1055 nm, by employing a volume Bragg grating in a retroreflector configuration as one of the cavity delimiters. Output powers in excess of 4.3 W were recorded with a spectral bandwidth of 5 GHz and an M(2) value below 1.3 over the whole tuning range.     

大幅度增加弛豫振荡频率来实现毫米级外腔半导体激光器的外腔机制转换

混沌外腔半导体激光器输出明显存在弛豫振荡特征,弛豫振荡频率小于外腔振荡频率时,外腔半导体激光器输出态是短腔机制;反之,外腔半导体激光器输出态是长腔机制.首先对比分析了弛豫振荡频率为5.6 GHz,腔长对频谱有效带宽的影响.然后同时调节注入电流和载流子寿命来大幅度地增加弛豫振荡频率.最后在弛豫振荡频率为40 GHz、腔长为毫米级(4—20 mm)时,实现由短腔机制到长腔机制的转换,进而分析了外腔反馈率和外腔长对外腔半导体激光器频谱带宽的影响.分析结果表明:短腔机制下,输出混沌态不稳定,0.1 mm的偏差就会导致混沌态与非混沌态之间的转化;长腔机制下,输出混沌态稳定,输出混沌区域较大,证明长腔机制下更有益于获得宽带连续的混沌区域.在弛豫振荡频率为40 GHz、外腔长度为毫米级时,实现了外腔半导体激光器的长腔机制,从而增大了高带宽混沌的参数空间.     

High-resolution cavity-tuned ringdown spectrometer using a narrow-bandwidth pulsed laser source

A novel method of cavity ringdown spectroscopy is proposed to achieve high spectral resolution with tunable narrow bandwidth pulsed lasers. We demonstrate a cavity-tuned ringdown configuration in which only a single cavity mode is kept excited near the carrier frequency of a narrow bandwidth pulse laser. This is done simply by making a cavity resonance actively track the frequency reference served by the cw injection seed of the pulsed laser source. We present the servo mechanism used in the cavity resonance tracking, reliable procedures for transverse mode matching, and the evidence of single longitudinal mode excitation. The spectrometer performance is tested to record weak molecular overtone features of acetylene around the wavelength of 570 nm, showing cavity tracking stability within 5-MHz uncertainty which overcomes the bandwidth limit of pulsed laser sources itself. PACS 42.62.Fi; 42.60.Da; 33.20.Kf     

Mode-locked fiber laser frequency-controlled with an intracavity electro-optic modulator

We demonstrate a mode-locked, erbium-doped fiber laser with its repetition frequency synchronized to a second fiber laser via an intracavity electro-optic modulator (EOM). With servo control from the EOM (bandwidth approximately 230 kHz) and a slower speed intracavity piezoelectric transducer (resonance at approximately 20 kHz), we demonstrate stabilization of the repetition frequency with an in-loop rms timing jitter of 10 fs, integrated over a bandwidth from 1 Hz to 100 kHz. This represents what is to our knowledge the first time an EOM has been introduced inside a mode-locked laser cavity for fast servo action and the lowest timing jitter reported for a mode-locked fiber laser.     

双反馈半导体激光器的混沌特性研究

实验利用双反馈半导体激光器获得了关联维数为3.8的高维混沌光.同时对比分析了双反馈与单反馈两种不同模式产生混沌的区别.结果表明：在反馈强度均为-26 dB时,双反馈产生混沌的关联维数高于单反馈产生混沌的关联维数2.6;双反馈可获得带宽为11 GHz的混沌光,为单反馈产生混沌带宽5.5 GHz的两倍.当双反馈的两个外腔长度不相等时,混沌的自相关曲线能很好的隐藏外腔长度信息,可提高混沌通信的保密性. 关键词： 双反馈 半导体激光器 混沌 带宽     

The properties of a GaAs-GaAlAs traveling-wave laser amplifier

The reflectivity of the cavity mirrors of a GaAs-GaAlAs DH semiconductor laser are reduced to 1*10^-4 by sputtering a film Si₃N₄. The gain of traveling-wave laser amplifiers is measured. The highest gain is about 25 dB. The dependence of gain on the injection current is measured. The measured frequency bandwidth shows the great advantage over other types of semiconductor laser amplifiers.     

Continuous-wave singly resonant optical parametric oscillator based on periodically poled RbTiOAsO(4)

We report a continuous-wave optical parametric oscillator (OPO) based on periodically poled RbTiOAsO(4) (PPRTA). The singly resonant OPO, which is located within a Ti:sapphire laser, has a high-finesse signal cavity and delivers a maximum output power of 270 mW to the nonresonant idler wave at 2.92mum , through a 4.5-mm PPRTA crystal. For room-temperature operation and a crystal with a 30-mu;m grating period, pump tuning over 838-848 nm results in OPO tuning over 1.13-1.27mum (signal) and 2.53-3.26mum (idler), limited by the bandwidth of optical coatings. PPRTA exhibits thermal properties superior to those of periodically poled LiNbO(3) .     

Direct intensity modulation of a rectangular ring laser with bidirectional lasing characteristics

The direct intensity modulation of a three-guide coupled rectangular ring laser having bidirectional lasing characteristics is reported for the first time. The rectangular laser cavity consists of four low loss total internal reflection mirrors and an output coupler made out of three passive coupled waveguides. The laser is fabricated using a total cavity length of 580 μm with active section lengths of 250 μm. For both the clockwise and counterclockwise circulating directions, a lasing threshold of around 38 mA is obtained at room temperature under continuous wave operation. A maximum 3-dB modulation bandwidth of approximately 3.2 GHz is observed in both circulating directions.     

Untersuchung der Differenzfrequenzen zwischen zwei Lasern

The frequency stability of He-Ne-Lasers was investigated by heterodyning two free running laser oscillators. Measurements were performed in a laser device of high mechanical stability protected against acoustical noise. For single mode operation the stability and spectral purity of the laserfrequency was found to be well defined by the constancy and bandwidth of the beat frequencies. In multimode operation beat frequencies were found which were nearly independent from the oscillator cavity length. They were produced by inevitable nonlinearities in the electronic equipment. For pointing out this effect more clearly, an additional nonlinear element was introduced into the electronic circuit. The additional nonlinearity was found to produce the same beatfrequencies as observed before, but with higher amplitudes. Presence of these second order beats may lead to misinterpretation of the frequency stability. From the minimum obtained beat frequency of 200 c/s in single mode operation it was concluded that a minimum laser bandwidth of smaller than 200 c/s was realized.