Zhenghe Sun

Tunable pulse-width, electro-optically cavity-dumped, rf-excited Z-fold waveguide CO2 laser

In this paper, an electro-optically cavity-dumped, rf-excited, Z-folded waveguide CO2 laser is presented. Theoretical studies on the laser output wave form and method to control laser pulse width and output power are made. In the experiment, a pulse width of a cavity-dumped laser can be changed from 12 to 32 ns. However, the corresponding peak powers reduce from 7000to2800W at a pulse repetition rate of 10kHz. The experimental results are consistent with the theoretical analyses.

Active and passive frequency stabilization for a Q-switched Z-fold radio-frequency-excited waveguide CO2 laser with two channels.

We report on passive offset frequency stability in free-running applications and active offset frequency stability achieved by use of a frequency-locking technique for a Q-switched Z-fold rf-excited waveguide CO2 laser with two channels. The laser structure of common electrodes and two channels has the advantage of compensating for the frequency variation caused by variations in temperature, cavity length, gas refractive index, and mechanical vibrations, so its offset frequency stability is higher than that of two separate lasers. In the experiments, the offset frequency shift was less than 6 MHz for 3 min in free-running mode. The technique of active offset frequency locking by counting was also introduced. The beat frequency shifting value was smaller than +/- 0.5 MHz in the long-term.

Study of frequency stabilization for electro-optical Q-switched radio-frequency-excited waveguide CO2 laser using build-up time method.

An electro-optical Q-switched RF-excited Z-fold CO(2) waveguide laser was designed, which can output a Q-switched laser and a cavity-dumped laser synchronously. The build-up time method is presented to stabilize the laser frequency. A closed-loop control system was designed to keep the laser oscillating at the peak of the gain curve by measuring the pulse build-up time continuously and controlling the cavity length. In the experiment, the variations for the pulse build-up time and cavity-dumped laser output power with time were recorded in a period of time. The frequency fluctuation is less than ±16 MHz.

Research on laser wavelength measurement with rotating Fabry–Perot mirror

Abstract. A method using rotating Fabry–Perot (FP) mirror to measure CO2 laser wavelength was developed. The variation of FP transmittance changing with laser incident angle was calculated theoretically and the variation curve was given. The calculation illustrates that the variation of FP reflectance with incident angle 0 to 30 deg has little effect on the transmittance of FP. In the experiments, the CO2 laser transmittance variation of FP was measured at a wavelength of 9.27 μm. To improve the measurement precision of the laser wavelength, the method using the centrosymmetric peaks of FP transmittance curve in the range from −20 to +20  deg of laser incident angle was proposed. The precision of the measurement is about 0.01 μm. The experiment result is consistent with theoretical analysis, which demonstrates the feasibility of the laser wavelength measurement using rotating FP method.

Study of Offset Frequency Locking and Active Frequency Stabilization for Two RF-Excited Waveguide CO 2 Laser With Common Ground Electrode

In this paper, we designed the offset frequency locking and active frequency stabilization system for the continuous-wave (CW) and electro-optical Q-switched RF-excited waveguide CO2 lasers to provide an ideal light source for coherent radar. The CW laser is used as a local laser, and the pulsed laser is used as a main laser, which can produce Q-switched and cavity-dumped laser synchronously. A closed-loop laser frequency control system was used to stabilize the Q-switched laser at the gain curve center frequency and to lock the two lasers at a selected heterodyne frequency. The system includes two parts: 1) pulsed laser frequency stabilization and 2) offset frequency locking. The frequency stabilization part can keep the Q-switched laser oscillating at the peak of the gain curve by measuring the pulse build-up time continuously and controlling the cavity length. The offset frequency locking circuits keep the heterodyne frequency around the selected frequency by measuring the frequency of the beat signals and controlling the CW laser cavity length. In the experiment, the long-term frequency shift of the pulse laser was measured to be less than ±16 MHz and the offset frequency fluctuation was less than ±2 MHz when the frequency control system was in a closed-loop operation.

Incoherent and coherent coupling for multi-slab solid laser

Optic field intensities of double and triple parallel slabs solid laser are numerically calculated. The results show that high beam qualities are difficult to obtain no matter coherent or incoherent output. In order to obtain high beam quality for mult-slab solid laser, we designed a new solid laser construction of radial slabs array according to the present condition for solid and RF excited radial array CO2 gas laser. The numerical calculated results show that this kind of laser can output high beam quality laser both coherent and incoherent cases. It is prospective to be a new research direction for high power, high beam quality, compact and scale solid laser.

Research on CO2 Laser Frequency Stabilization by Adjusting Grating Angle

A new frequency stabilization for CO2 laser with frequency selection by grating is presented in this paper. A closed-loop control system was designed to stabilize the laser frequency at the gain curve center by measuring the changing laser power continuously and fine adjusting the grating angle of the laser cavity. In the experiment, the long-term laser power and frequency shift of the CO2 laser 9P (10) line were measured to be less than ±0.035 W and ±7 MHz, respectively, when the frequency stabilization is in closed-loop operation. The CO2 laser frequency stability is up to 4.6 × 10−8. The frequency stabilization control system owns advantages of small volume, compact structure. It can be also used for other type of lasers.

Offset Frequency Locking for Pulsed CO2 Waveguide Laser with Two Channels

This paper studies the active offset frequency locking for the Q-switched/cavity-dumped z-fold RF excited waveguide CO2 laser with two channels. The method of frequency locking is simple and applicable not only for short pulse CO2 laser but also for many other kinds of short pulse lasers