Expensive Optical Elements Research Articles

A design of debris mitigation system for high-repetition-rate petawatt laser experiments

The shooting of high-power laser pulses on solid targets will generate a large amount of debris which can damage the expensive optical elements and impair the laser focusing quality. The existing and upcoming high-repetition-rate petawatt lasers which are able to deliver hundreds of shots in minutes would face more serious debris problems. In this work, we propose a high-speed-spinning multi-disc debris mitigation system. An optimization method based on Bayesian Optimization is developed to acquire the optimal parameters of the system.

Flattening laser frequency comb spectra with a high dynamic range, broadband spectral shaper on-a-chip.

Spectral shaping is critical to many fields of science. In astronomy for example, the detection of exoplanets via the Doppler effect hinges on the ability to calibrate a high resolution spectrograph. Laser frequency combs can be used for this, but the wildly varying intensity across the spectrum can make it impossible to optimally utilize the entire comb, leading to a reduced overall precision of calibration. To circumvent this, astronomical applications of laser frequency combs rely on a bulk optic setup which can flatten the output spectrum before sending it to the spectrograph. Such flatteners require complex and expensive optical elements like spatial light modulators and have non-negligible bench top footprints. Here we present an alternative in the form of an all-photonic spectral shaper that can be used to flatten the spectrum of a laser frequency comb. The device consists of a circuit etched into a silicon nitride wafer that supports an arrayed-waveguide grating to disperse the light over hundreds of nanometers in wavelength, followed by Mach-Zehnder interferometers to control the amplitude of each channel, thermo-optic phase modulators to phase the channels and a second arrayed-waveguide grating to recombine the spectrum. The demonstrator device operates from 1400 to 1800 nm (covering the astronomical H band), with twenty 20 nm wide channels. The device allows for nearly 40 dBs of dynamic modulation of the spectrum via the Mach-Zehnders , which is greater than that offered by most spatial light modulators. With a smooth spectrum light source (superluminescent diode), we reduced the static spectral variation to ∼3 dB, limited by the properties of the components used in the circuit. On a laser frequency comb which had strong spectral modulations, and some at high spatial frequencies, we nevertheless managed to reduce the modulation to ∼5 dBs, sufficient for astronomical applications. The size of the device is of the order of a US quarter, significantly cheaper than their bulk optic counter parts and will be beneficial to any area of science that requires spectral shaping over a broad range, with high dynamic range, including exoplanet detection.

Photovoltaic Concentration: Research and Development

Concentrator Photovoltaic (CPV) technology, by using efficient optical elements, small sizes and high efficiency multi-junction solar cells, can be seen as a bright energy source to produce more cost-effective electricity. The main and basic idea is to replace the use of expensive solar cells with less expensive optical elements made from different materials. This paper aims to give to the readers a rapid and concise overview of CPV and the main characteristics to be considered when designing a CPV system. It reviews the main optical configurations presented in the literature, their advantages and drawbacks, as well as the recent progress in the concentration ratio and the major performances achieved in the field. The paper considers the more recent works, their optical designs, as well as their optical and electrical performances. It also relates the major achievements on the industrial side with the major milestones in CPV developments.

On-line optical measurements of the mass concentration of aerosols in ecology

The article provides a brief retrospective of methods for determining the dust content of atmospheric air and their modern implementation in optical particle counters. It is shown that the operational control of the mass concentration of the dispersed component of the atmosphere is now highly relevant. Unlike the classic, the most accurate "weight method", the use of photoelectric particle counters allows you to measure the mass concentration of aerosol pollution by fractions of the dust component. Such measurements are much more informative in ecology, since they take into account the specifics of the harmful effects of anthropogenic aerosol on humans and animals.The features of the optical method of detecting and analyzing particles by modern aerosol counters that have laser light sources in the registration circuits are considered. The heterogeneity of the luminous flux, which is natural for lasers and leads to considerable measurement errors, forces developers to look for ways to take into account or neutralize this effect not with expensive optical elements, but with the help of microprocessors. This article describes an original method for registering particles in an aerosol counter using two photo-detectors. The laser light reflected from the particles under study is converted by these photosensors into electrical pulses, which are analyzed by a signal matching circuit using a specific algorithm.The prototype of the portable device made by the authors of the article, which implements this method, was compared with the classical “weight method” to determine the mass concentration of particles in a special aerosol chamber. Within the framework of measurement errors, a good agreement between the obtained data is shown. This meter, which is the first domestic analyzer of air dispersed composition, allows you to transmit the received information in a digital form via wireless networks to monitor the environmental situation in various regions. In relation to this photoelectric device, a program has been developed for creating a network for monitoring the dust content of an air basin, a fragment of which is displayed on the website of the global international association Enterprise Europe network, which includes enterprises in seventy countries of the world.

Experimental study of depolarization of laser radiation by fiber optic elements

At present, in polarization-based optical fiber sensors the optical fiber is used both as a sensitive element (SE) and as fiber-optic communication lines (FOCL) for transmission of an optical signal. In such sensors, the polarization axes of the optical radiation source (ORS) and SE need to be aligned. However, FOCL elements located between the ORS and SE introduce their own polarization distortions due to the anisotropy of the optical properties of the fiber resulting from bending deformations of a random nature. This leads to a decrease in the accuracy and repeatability of the polarization sensor (PS) measurements. The proposed method of polarization correction consists in depolarization (transformation into circular polarization) of optical radiation by placing coils with an optical fiber between the ORS and SE, and certain parameters: the diameter of the coil, the number of turns and the angle of rotation of the coil relative to the plane of polarization of the ORS. This method allows one to exclude from the optical setup expensive optical elements (for example, quarter-wave plates) and simplify the design of the sensor / measuring device. In the course of experimental studies it was found that in this way it is possible to reduce the polarization distortion from the initial 17 dB to 1.6 dB.

Method and apparatus for scanning, stitching and damping measurements of a double sided metrology inspection tool

A system for inspecting specimens such as semiconductor wafers is provided. The system provides scanning of dual-sided specimens using a damping arrangement which filters unwanted acoustic and seismic vibration, including an optics arrangement which scans a first portion of the specimen and a translation or rotation arrangement for translating or rotating the specimen to a position where the optics arrangement can scan the remaining portion(s) of the specimen. The system further includes means for stitching the scans together, thereby providing both damping of the specimen and the need for smaller and less expensive optical elements.