Study On Small Signal Gain Measurents System For Continuous Wave HF/DF Chemical Laser

Since its birth, chemical lasers have been the star in the field of high power lasers,especially in military applications. As a key parameter of continuous wave chemicallasers, small-signal gain(SSG) coefficient have great influence on laser characteristics,including threshold condition, performance of gain generator and laser resonator design.So it is important to study the magnitude and distribution of SSG coefficient boththeoretically and practically. From the invention of CW chemical lasers to now, themeasurement method of SSG coefficient has always been an important study field.Researchers have proposed many ways, but most of them can only make singlemeasurement, and the equipments are also low integrated.An integrated system is built through the fulfillment of the thesis which can realizeboth the magnitude and one-dimensional distribution measurement of the SSGcoefficient. Compared with the former devices, our system has many advantages. It hasstable performance, compact structure with total size of 60cm 60cm, and high level×ofintegration.In this article, detailed study is made on the probe laser, optical system and dataacquisition and processing sub system. Probe laser is line selected HF laser in Littrowconfiguration. By the optimization of laser cavity parameters, stable fundamental modeis obtained with 2mm waist diameter and 1.8mrad divergence angle. By step motor,auto spectra line selection is realized, and 11 lines were obtained. For optical system, allthe mirrors are reflected to avoid chromatic aberration, a beam splitter cube isintroduced to make the probe laser double pass the gain medium, which can simply thebeam path and increase measurement precision. A high level parallelism isdemonstrated by ray tracing simulation. The data acquisition and processing sub systemis realized by virtual instruments. Many functions can be realized, including dataacquisition display, data save and read, signal phase lock amplification, calculation ofSSG coefficient and scan mirror control.Take 532nm laser as probe beam, the SSG measurement system is testified byoptical filters with transmittance of 32%, 50% and 90% respectively, which aresupposed as the gain medium. The deviations from theoretical value are 1.2%, 6.8% and9.5% in fixed point measurement, and 3.5%, 8.9% and 5.7% in scanning scheme. Afterthe validation of the measurement system, it is used to take practical measurement of adischarge-driven supersonic HF/DF chemical laser. Gain curves of 5 spectral lines aremeasured, the results agree well with lasing experiment.