Subsurface damage (SSD), having a great impact on the laser-induced damage threshold (LIDT) of ultra-smooth optics applied in high-power laser systems, should be tightly controlled. An improved total internal reflection microscopy (TIRM), combined with digital image processing techniques, is proposed to quantitatively inspect SSD. With the characteristic that there is a relatively small depth of field (DOF) for a microscope at high magnification (50×), a series of SSD images are captured along with the microscope focusing at different depths under the surface by means of micro-focusing control. The definition of each image is calculated through wavelet transformation. By simulation, the relationship between the definition of TIRM images and the depth of the SSD has been established. According to the definition curve, the SSD depth is acquired. Fused silica glasses polished after fine grinding are measured non-destructively by our TIRM setup. The results show that the improved TIRM is a useful method to evaluate SSD. It is helpful to improve the efficiency of optical fabrication.

An optical characterization method with high spectral resolution for broadband, multilayer dielectric gratings working at the −1st reflection order is demonstrated in this paper. The diffraction-efficiency measurement setup for the broadband gratings with high efficiencies mainly consists of a double-light-path system with a monochromator as the illumination source and an automatic rotation stage for incident and diffraction angles adjustment. Two typical practical difficulties, namely (1) the mismatch between the spot size of diffracted light and the limited detector aperture and (2) the shared propagation path between the incident and diffracted light at the Littrow angle, were well solved. A fabricated multilayer dielectric grating was measured on the established measurement setup. Diffraction efficiencies greater than 90% in the wavelength range from 763 to 852 nm were obtained with an average relative deviation less than 1.0%. At the moment, the wavelength resolution is 1 nm and the angle resolution is 0.2 deg. The high-resolution broadband diffraction spectrometry testing method is applicable to characterizing broadband pulse compression gratings in the laser systems.

In general, k lenses with different materials can achieve at most ( k + 1 ) color correction ( k ≥ 2 ). A superachromat containing three lenses is designed to achieve five-color correction in the 600–1600 nm waveband, where the maximum chromatic focal shift is controlled within 1/100,000 of the focal length, achieving an almost unprecedented result. Conditions for lens power combination of three thin lenses in contact are first derived based on the Buchdahl dispersion equation; then a metric is introduced to verify the five-color correction, and a correction method is proposed to improve the refractive index fitting accuracy of the Buchdahl model from ∼ 10 − 3 to ∼ 10 − 7 . By traversing 197 ecofriendly glass materials in the CDGM glass library iteratively, 113 initial structures are obtained in only 61.75 s, from which the structure with the minimum chromatic focal shift is selected to be optimized with Opticstudio. By setting up required operands, the final structure being within the diffraction limit in a field of view of ± 0.05 ∘ is obtained within only 6 s, where the maximum longitudinal chromatic aberration is close to the maximum chromatic focal shift. We provide a complete theoretical basis and important guidance for designing broadband superachromats with ( k + 2 ) color correction using only k lenses and the smallest chromatic focal shift, and based on the theories, we have developed a broadband interferometer.

High-power laser system has a requirement for the medium and low spatial wavefront errors of the transmitted wavefront of the spatial filter, which is a spherical lens with long focal length (> 10 m) and large aperture (> 400×400 (mm)). Two interferometric methods are analyzed and compared for testing the medium and low spatial wavefront errors of the long focal length lens with an instantaneous interferometer, using large -aperture plane mirror and concave mirror as retroflectors, respectively. The two kinds of beam path -arrangements are designed using ray tracing method. Wavefront aberration and modulation transfer function are used as merit functions. The reason for their different ability to test the wavefront is also analyzed. To evaluate the -feasibility of test methods, tolerances analyses are performed to determine the tolerances demanding the fabrication and assembly of each optical element. It is proved that a relatively short optical path with a large aperture concave mirror is satisfied for testing the medium and low spatial wavefront errors of the transmitted wavefront of the spatial filter.

The measurement of the spectral diffraction efficiencies of a diffraction grating is essential for improving the manufacturing technique and for assessing the grating’s function in practical applications. The drawback of the currently popular measurement technique is its slow speed due to the hundreds of repetitions of two kinds of time-consuming mechanical movements during the measuring process (i.e., the rotation of the mechanical arm to capture the light beam and the mechanical variation of the output wavelength of the grating monochromator). This limitation greatly restricts the usage of this technique in dynamic measurement. In this manuscript, we present a motionless and fast measurement technique for obtaining the spectral diffraction efficiencies of a plane grating, effectively eliminating the aforementioned two kinds of mechanical movements. Herein, the proposed solution for removing the first kind of mechanical movement is tested, and the experimental result shows that the proposed method can be successfully used to measure the plane transmission grating’s spectral diffraction efficiencies in the wavelength range of 550-750 nm. The method for eliminating the second kind of mechanical movement is not verified in this manuscript; however, we think that it is very straightforward and commercially available. We estimate that the spectral measurement can be achieved on a millisecond time scale by combining the two solutions. Our motionless and fast measuring technique will find broad applications in dynamic measurement environments and mass industrial testing.

Ion beam sputtering is widely utilized in the area of ultra-high precision fabrication, coating, and discovering the microworld. A pulsed ion beam (PIB) can achieve higher material removal resolution while maintaining traditional ion beam removal performance and macro removal efficiency. In this paper, a 0.01 s pulse width beam is used to sputter atom layer deposition (ALD) coated samples. The nano-scale phenomenon is observed by high-resolution TEM. The results show that when the cumulative sputtering time is less than 1.7 s, the sputtering removal of solid by ion beam is accompanied by a nonlinear effect. Furthermore, the shortest time (0.05 s) and lowest thickness (0.35 nm) necessary to remove a uniform layer of material were established. The definition of its nonlinear effect under a very small removal amount guides industrial ultra-high precision machining. It reveals that PIB not only has high removal resolution on nanoscale, but can also realize high volume removal efficiency and large processing diameter at the same time. These features make PIB promising in the manufacturing of high power/energy laser optics, lithography objective lens, MEMS, and other ultra-high precision elements.