Multiple surfaces transform interferometery is a preferred technology for surface profile and index homogeneity measurement using a Fourier based analysis method combined with phase-shifting interferometer. As a four-surface cavity for example, the surface form and index inhomogeneity of the parallel plate are deduced by extracting the information from the corresponding interference frequency. The errors of surface form and index homogeneity are simultaneously simulated and analyzed with different sampling buckets. The results show the feasibility and high precision of this approach compared with traditional methods.
We investigate the dynamic processes of the Nd:YAG pulse laser ablation of fused silica by ultrafast time-resolved optical diagnosis with a nanosecond time resolution. The evolution process of plasma expansion in air and shock waves propagation in the bulk are both obtained with spatial and temporal resolutions. Laser-induced damage in the bulk of fused silica with filaments and shock waves are observed. Thermoelastic wave, mechanical wave, and shock wave dependence on the laser fluence and intensity of the plasma are analyzed. The shock pressure P and temperature T calculated through the measured shock velocity D and the Hugoniot data of fused silica are measured.
Abstract We report a super-resolution imaging microscope adopting the spatially structured illumination that is able to providing super-resolution and high signal noise ratio images of submicron defects on the surface and subsurface of optical components in this research. Employing the combination of structured illumination microscopy (SIM) and reflective light scattering (RLS) microscope, RLS-SIM extends the transmission band of optical transfer function of the RLS microscopy, thereby improving resolution and breaking the conventional Rayleigh diffraction limit. With 633 nm illumination light source and 100×/0.8 objective, the reconstructed RLS-SIM image of natural defects on the optics component reveals the lateral limit resolution ~296 nm, a factor of 1.63 than that of the normal bright-field microscopy with the same parameters. Moreover, compared with traditional microscope (bright-field/dark-field) and SEM images, the RLS-SIM images are demonstrated to present the finer structures of submicron digs and scratches formed in the optics manufacturing process which have a good application prospect in the research of damage mechanism of precision optical components and the upgrading of processing technology.
As the development of high powered laser system, the measuring accuracy of optic’s transmissivity need to be improved in order to guarantee all the optics’ quality. This paper analyses all the factors which largely influence the testing accuracy of optics transmissivity when using the spectralphotometer. Experiments are carried out to verify all the deduced results. The results show that the accuracy of wavelength, error of incident angle and divergence of measuring beam would influence the testing result of transmissivity, and the divergence of measuring beam would contrubite to the largest error. Therefore, the testing accuracy could be greatly increased by decreasing the divergence angle of measuring beam.
Parallelism is an important parameter of plane glass in high power solid-stat lasers. In this paper, a method for parallelism measurement is proposed. This method is based on total least squares(TLS) to fit wavefront into plane, the parallelism can be calculated by the included angle between planes. Furthermore, with tri-dimensional ray-tracing method, larger aperture plane glass can be measured with smaller interferometer at oblique incidence. A comparison test about parallelism measured at 0° and oblique incidence is set up to verify the accuracy of this method.
This paper investigates the high-power laser-induced damage of two types of single-layer SiO2 thin films on K9 substrate, which are respectively deposited by IBSD technique and sol-gel technique, and have the same substrate parameters and the same film thickness. They were tested by surface thermal lensing technique to obtain the thermal absorbance and the dynamic response. The results show that the laser-initiated damage threshold of Sol-Gel SiO2 thin film is far higher than that of IBSD SiO2 thin film. And combined with threshold measurement and the microscopic observation, this paper well explains in detail the threshold difference between Sol-Gel SiO2 and IBSD SiO2 thin films.
Due to external cavity, the external-cavity diode laser (ECDL) is sensitive to the harsh environment. It can serve as a very convenient tool for measuring or comparing acoustic responses and analysis of acoustic insulation characteristics of materials and mechanical structure. Focused on the ECDL, improvement of the laser acoustic responses and suppression of the laser system drift are critical. But the acoustically-induced vibration coupled with complex disturbance will contribute to the frequency fluctuation, therefore it is difficult to investigate the dynamic response characteristics of laser frequency to acoustic signals separately. In order to decouple the acoustic response from environmental noise and to reduce system drift, a frequency stabilization system by virtue of grating feedback and current feedback is demonstrated with the a wide-bandwidth loop. After recording the system response, the amplitude-frequency characters are achieved through fast Fourier transform (FFT). After analyzing the correlation of the laser frequency fluctuation and the acoustic stimulant signal's frequency, the acoustic dynamic response characteristics of the ECDL is depicted experimentally. By contrasting the acoustic response characteristics of the ECDL with or without the acoustic proofing case, the acoustic insulating effect could be mapped directly. The experimental results show that the acoustic proofing case can not be remained valid for all frequency bands effectively. It can also act as the experimental criteria for optimizing the design of laser mechanical structures and acoustic insulation systems. Furthermore, this optical system could be employed as a detector extending to acoustic sensing or acoustic precise measurement.
The focal length is one of the important parameters in the optical element, and the high precision measurement of the focal length has become a key problem in the processing and use of the optical element. The laser differential confocal length measurement system is introduced, and the uncertainty of the two sets of focal length measurement is evaluated. The relative error (K = 2) is better than 4.77×10-5, and the relative error is 0.00025%.
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