一种连续Nd：YAG激光锁模的新技术

本文首次报道了在连续运转的Ｎｄ：ＹＡＧ激光器上通过移动腔镜实现锁模的实验研究。获得平均宽度为６０ｐｓ的锁模脉冲序列。文中提出了实验结果的初步解释，表明这种锁模现象是一种增强的自锁模。     

The effect of hard mode locking in a dye laser

The influence of the relaxation time of a saturable absorber on the dynamics of a quasi-continuous ring laser is investigated. It is shown that in a dye laser with a fast absorber, bistability arises; thus two multimode regimes coexist. The regime of shallow stochastic modulation is established spontaneously. Transition to the mode-locking regime accompanied by a sharp increase in the number of generated modes is feasible only under the action of an initiating pulse (hard mode locking). The analytical criterion for hard locking has been obtained. If the criterion is not satisfied, the only stable regime of a laser is mode locking. In this case the transient process is the longer the smaller the relaxation time of a saturable absorber.     

Passive mode locking of the continuous wave DCM dye laser

The first passive mode locking of the continuous wave (cw) DCM dye laser is reported. Subpicosecond pulses as short as 0.68 ps were obtained over the spectral region from 655 to 673 nm from a simple linear cavity with no dispersion optimisation. The dye 1,3 Diethyl 4,2 quinolythiacarbocyanine iodide (DQTCI) was used as the saturable absorber.     

CW diode pumping and FM mode locking of a Nd: KGW laser

We have demonstrated cw diode end pumping of Nd: KGW, a novel solid-state gain medium, with up to 30% conversion efficiency into near-TEM₀₀ (M² < 1.05) output at = 1.067 µm for a pump level of 2.7 W. The slope efficiency was limited by intracavity reflections to 36%; however, direct comparison to a similar Nd:YAG laser indicates the same intrinsic slope efficiency of 60%. FM mode locking of this laser at 200 MHz has produced 12 ps pulses (compared to 16 ps for Nd: YAG), although an intracavity etalon was required. Considerable reduction in pulse width is possible (the line width limit is 0.5 ps) but different techniques may be necessary. Spatial hole burning was evident in both the 120 GHz free-running spectrum and the etalon-limited mode-locked spectrum.     

Active mode locking of a high pressure CW waveguide CO2 laser

In this paper, we report on a new concept for active mode locking of lasers. It has been successfully applied to a cw waveguide CO₂ laser and pulse widths as short as 2 ns have been obtained.     

Passive mode locking of DCM and Rhodamine 101 flashlamp-pumped dye laser systems

The passive mode locking of the laser dyes DCM and Rhodamine 101 which operate in similar spectral regions, has been carried out in a simple flashlamp-pumped system. Pulses of 5 ps tunable from 618 nm to 693 nm with peak powers in excess of 5 MW have been obtained. Several suitable saturable absorbing species have been identified.     

Theory and experiment of CW dye laser injection locking and its application to second harmonic generation

High-power single-mode operation of a cw ring dye laser has been obtained by injection of cw single-mode radiation. The intracavity power of this system was used to generate tunable single-mode uv radiation by frequency doubling in a temperature phase-matched ADA crystal: up to 45 W intracavity fundamental power and up to 70 mW extracted uv power have been observed. A theoretical treatment of the injection locked cw ring dye laser system is given for the stationary state. Expressions for the intracavity intensities as a function of the small-signal gain and the saturation intensity are derived.     

Efficient single mode operation of a CW ring dye laser with a Mach-Zehnder interferometer

Stable single mode operation of a ring dye laser is obtained with the combination of a Mach-Zehnder interferometer (MZI), three plate birefringent filter, a single thin etalon and a unidirectional diode. The MZI eliminates the fractional insertion loss due to beam walk-off and distortion which an intracavity etalon must introduce in order to select single frequency operation. We experimentally demonstrate the low insertion loss, single mode stability and frequency tuning of a ring dye laser using a specially designed, compact MZI. Finally, we propose MZIs with no coatings, which should permit extremely low loss broadband operation.     

CW dye laser emission beyond 1000 nm

We report CW dye laser emission extending the spectral range up to 1020 nm with three carbocyanines. These dyes are pumped by the infra-red lines of a krypton laser. They have a fairly good stability in time. 50 mwatt tuned output power has been obtained at 1000 nm.     

连续波环形染料激光器的单向运转特性

本文讨论了连续波环形染料激光器的单向运转特性。采用改进的Ganiel速率方程模型,分析了在单向运转条件下泵浦光通量、染料分子密度等参量对激光光通量、激发单重态粒子集居数密度以及增益的影响;揭示了在连续波环形染料激光器中单向运转条件下存在粒子集居数密度的非对称性、激光光通量与激活介质内空间位置的相关性和增益峰值波长的扫描现象。本文给出了数值计算结果。     

Opto-acoustic spectroscopy with a visible CW dye laser

The first use of a tunable visible laser in conjunction with an opto-acoustic cell is described. By using a longitudinal resonance of the gas cell NO₂ can be detected around 10 p.p.b., the same order of detectivity as in the infrared. The use of the technique for studying photodissociation in the visible and u.v. is discussed.     

An alternate model of CW dye laser intracavity absorption

A new model is presented for intracavity absorption in a CW multimode dye laser based on the similarity between the laser and a self-quenched super- regenerative oscillator. The model suggest that the primary interaction mechanism between the atomic absorber and the laser is through a modification of the background radiation level from which the oscillation builds up. Numerical calculations are carried out leading to a prediction of the spectral line shape to be observed in intracavity absorption as well as the dependence of the signal on absorber density and pump power.     

Line shape studies in CW dye laser intracavity absorption

The line shape of the signals observed by intracavity absorption in an atomic beam of barium is studied as a function of absorber density. Complex structure is observed consisting of both absorption and enhancement features. Comparison is made with models of intracavity absorption, and it is concluded that the rate equation model in its present form does not explain the structure. On the other hand the super-regen model does seem able to partially account for the observed structure. The complexity of the line shape will directly affect those workers who are using intracavity absorption as a spectroscopic technique.     

CW dye laser operation at 200 W pump power

A continuously operating jet stream dye laser was pumped by a multiwavelength-multimode argon-ion-laser with a pump power up to 200 W. Rhodamine 6G-chloride was dissolved in a water-polyvinylalcohol-ammonyx solution. The dye laser was prism-tunable between 560 and 650 nm with maximum output power at 600 nm. The maximum output power of the cw dye laser was 43 W without tuning element and 33 W with a prism placed inside the cavity. Operation of a jet stream dye laser with a pump power higher than 200 W and an efficiency of about 30% seems to be possible.     

Frequency locking of a dye laser using adsorbed atoms

Frequency locking of a dye laser to atomic lines is obtained by using atoms adsorbed on an intracavity glass surface. This effect is attributed to the selective transmission of the interface due to anomalous refractive index.     

Prism tuner for single frequency operation of CW dye laser

A cw dye laser capable of single longitudinal mode operation and linear reproducible wavelenght tuning over a relatively wide spectral range is described. By employing a novel scheme of four intracavity highly dispersive Abbe prisms output powers of 5 mW with a linewidth less than 30 MHz for an input power of 700 mW have been obtained.     

Fourier domain mode locking pulse fiber laser

A novel pulse fiber laser is proposed based on the modulation of the lasing wavelength. Different from conventional amplitude or phase modulated mode-locking fiber lasers, the proposed fiber laser is with a so-called Fourier domain mode locking (FDML) operation (i.e., the cavity round-trip time of the optical pulse should match the period that the open time window of the tunable filter appears for the lasing wavelength or its harmonics). An FDML pulse fiber laser with a cavity round-trip frequency of 19.46 kHz is demonstrated and optical pulses with repetition rate of 19.46 kHz are achieved when the wavelength modulation frequency is 9.73 kHz.     

A single mode flashlamp-pumped dye laser

A flashlamp-pumped dye laser capable of single transverse and longitudinal mode operation is described. The maximum untuned power output is 2 MW cm^-2, TEM₀₀ mode. By employing three intracavity Fabry—Pérot etalons, a minimum spectral width of 4 MHz, stable to within 12 MHz, has been obtained.     

Saturated absorption experiments using a free running CW dye laser

The hyperfine structure of some new iodine lines has been observed over the tuning range of Rhodamine 6G (5800–6200 Å), using a free running, single mode cw dye laser. The resolution obtained in this experiment allowed to calculate the hyperfine constants of the excited state (³π₀⁺) of iodine with an accuracy of 2% for the quadrupole coupling constant and 50% for the magnetic one.     

Direct absorption spectroscopy using a rapidly tunable CW dye laser

Using a recently developed electronically tunable cw dye laser, the spectrum of an absorption sample could be obtained and repeatedly scanned every 10 μsec. The system is potentially capable of monitoring spectral changes in times as short as 10^?7 sec.