In order to research the influence on the beam transmission properties due to the different time intervals in the high-power pulsed transversely excited atmospheric CO2 laser with unstable resonator, the finite element analysis of thermodynamics instantaneous method are adopted to analyze the mirror thermal deformation irradiated by the high-power laser beam. The mirror thermal deformation is fitted by Zernike polynomials. Then the angular spectrum propagation theory of diffraction is used to calculate the far-field transmission properties. The simulation results show that with the decrease in the time interval between each pulse, the mirror temperature and thermal deformation gradually increase, and peak power and the average energy density decrease, and beam broadens. With the 500 Hz repetition rate relative to the 10 Hz repetition, the peak intensity decreases almost 40%; the optical spot broadens about 60%. When the repetition rate is larger than 100 Hz, the surface of mirror will have obvious deformation, which will cause apparent degradation in the optical beam quality for the far-field transmission.

We develop a new algorithm to evaluate the thermal features of a rubidium-vapor cell and a cesium-vapor cell pumped by the laser diode. The theoretical model is based on the principles of both heat transfer and laser kinetics. The obtained population density distribution and the radial temperature distribution are analyzed for both types of cells. It is thought that the theoretical results are logically reasonable and the mathematical precision is satisfactory in designing a real diode-pumped alkali laser (DPAL). The methodology is valuable in the construction of a high-powered DPAL in the future.

A method is presented for in situ resolution calibration of multiple feedback interferometers (MFIs) using two lasers with different feedback levels simultaneously. The laser with weak optical feedback level generates half-wavelength optical fringes, whereas the laser with strong multiple feedback level generates optical nano-fringes. By using this method, the number of displaced optical nano-fringes can be easily counted, and the resolution of the MFIs can be accurately determined. The integrated MFIs can be used to measure displacements and calibrate other displacement sensors.

Self-mixing interferometry (SMI) based on nanometer fringes and polarization flipping is realized. The interferometer comprises a single-mode He-Ne laser and a high-amplitude reflectivity feedback mirror. The nanometer fringes are obtained by tilting the external feedback mirror. The fringe density is 35 times higher than that derived with conventional two-beam interference, and each fringe corresponds to a \lambda/70 displacement in external cavity length. Moreover, polarization flipping occurs when the external feedback mirror moves in the opposite direction. Such movement can be used to easily distinguish displacement direction. Experimental results show an optical resolution of displacement measurement of 9.04 nm with a range of 100 μm. The proposed SMI presents promising application prospects in precisely measuring displacement and calibrating other micro-displacement sensors because of its optical wavelength traceability.

A pulsed chemical oxygen-iodine laser (COIL) using atomic iodine generated by volumetric discharge of CH3I is developed and tested. COIL with a gain length of 60 cm is energized by a square pipe-array jet singlet oxygen generator with basic hydrogen peroxide pumping circulations and operated at subsonic gas flow. Maximum output energy of 4.3 J, pulse duration of 50 μs, specific energy extraction from the active medium of 2.0 J/L, and the maximum chemical efficiency of 12.5% are achieved at a chlorine flow rate of 55 mmole/s.

Displacement sensor based on the polarization mixture and the cavity tuning of the orthogonal polarized He-Ne laser 1.15 \mu m is presented. The power tuning curves of He-Ne laser are irregular, and it is difficult to measure the change in cavity length. The distortion of the curves is caused by the higher relative excitation compared with the He-Ne laser at 633 nm. In view of its potential for the wider displacement measuring range, a new method of displacement sensing is developed. Experiments show that displacement measuring stability based on the method of the polarization mixture is better than that of the power tuning curves. The displacement sensor achieves the measuring range of 100 mm, resolution of 144 nm, and linearity of 7 \times 10^{ 6}.

The cavity tuning characteristics of orthogonally polarized dual-frequency He-Ne laser at 1.15 \mu m are presented. Vectorial-extension model based on semi-classical laser theory reveals that cavity tuning characteristics are related to beat frequency, relative excitation, and type of Ne isotope. Distortions of cavity tuning curves become moderate with the increase of beat frequency because of the weakening of the crosssaturation effect. Distortions are enhanced with the increase of relative excitation because of the combined action of the self-saturation and cross-saturation effects. By adopting dual-isotope Ne instead of monoisotoplic Ne, distortions are reduced because of the misalignment between peaks of the self-saturation and net gain coefficients. The theoretical calculations are in good agreement with the corresponding experimental results.

A novel precise force measurement based on a Y-shaped cavity dual-frequency laser is proposed. The principle of force measurement with this method is analyzed, and the analytic relation expression between the input force and the change in the output beat frequency is derived. Experiments using a 632.8-nm Y-shaped cavity He-Ne dual-frequency laser are then performed; they demonstrate that the force measurement is proportional to a high degree over almost five decades of input signal range. The maximum scale factor is observed as 5.02 \times 10^9 Hz/N, with beat frequency instability equivalent resolution of 10^{-5} N. By optimizing the optical and geometrical parameters of the laser sensor, a force measurement resolution of 10^{-6} N could be expected.