Process for Production of High Efficiency Volume Diffractive Elements in Photo-Thermo-Refractive Glass

A novel process is proposed for the volume diffractive element (Bragg grating) fabrication in photosensitive silicate glasses doped with silver, cerium, fluorine, and bromine. The process employs a photo-thermo-refractive (PTR) glass of high purity exposed to ultraviolet (UV) radiation of a He--Cd laser at 325 nm followed by thermal development at temperatures from 480.degree. C. to 580.degree. C., preferably at 520.degree. C., from several minutes to several hours. Absolute diffraction efficiency up to 95% was observed for 1 mm thick gratings. Maximum spatial frequency recorded in PTR glass was about of 10,000 mm.sup.-1. No decreasing of diffraction efficiency were detected at low spatial frequencies. Original glasses were transparent (absorption coefficient less than 1 cm.sup.-1) from 350 to 4100 nm. Induced losses in exposed and developed glass decreased from 0.3 to 0.03 cm.sup.-1 between 400 and 700 nm, respectively, and did not exceed 0.01-0.02 cm.sup.-1 in the infrared (IR) regi

High Efficiency Volume Diffractive Elements in Photo-Thermo-Refractive Glass

Novel volume holographic elements were made from Bragg diffractive gratings in photo-thermo-refractive (PTR) glass with absolute diffraction efficiency ranging from greater than approximately 50% up to greater than approximately 93% and total losses below 5%. Both transmitting and reflecting volume diffractive elements were done from PTR glasses because of high spatial resolution enabling recording spatial frequencies up to 10000 mm.sup.-1. The use of such diffractive elements as angular selector, spatial filter, attenuator, switcher, modulator, beam splitter, beam sampler, beam deflectors controlled by positioning of grating matrix, by a small-angle master deflector or by spectral scanning, selector of particular wavelengths (notch filter, add/drop element, spectral shape former (gain equalizer), spectral sensor (wavelength meter/wavelocker), angular sensor (pointing locker), Bragg spectrometer (spectral analyzer), transversal and longitudinal mode selector in laser resonator were de

Process of production of high efficiency diffractive and refractive optical elements in multicomponent silicate glass by nonlinear photo ionization followed by thermal development.

Apparatus, methods and systems for production of high efficiency refractive and diffractive elements by providing a photo-sensitizer fi-ee multicomponent glass, exposing the multi component glass to pulsed laser radiation to produce refractive indexed modulation, and heating the exposed multicomponent silicate glass to produce the high efficiency refractive and diffractive elements. The pulsed laser radiation is infrared femtosecond pulses to ultraviolet nanosecond pulses which provide ionization of glass matrix. The multicomponent glass is a photosensitive glass with high transparency in ultraviolet spectral region, e.g. silicate glass which includes silver, fluorine and bromine and does not contain photosensitizers such as cerium and antimony, PTR glass, cerium free PTR glass and cerium + antimony free PTR glass

Laser Pulse Temporal, Spectral And Spatial Shaping Devices Based On Volume Diffractive Gratings With Variable Parameters

Recent invention of longitudinally chirped volume Bragg gratings has dramatically changed a design of high power femtosecond lasers. Replacing of bulky pairs of conventional surface gratings with compact and robust chirped volume Bragg gratings for stretching and compression of laser pulses in chirped-pulse-amplification systems enabled decrease of size and weight of those systems by several times. This patent application enables substantial increase of stretching time and compression to shorter pulses along with more complex shaping of laser pulses in both temporal and spectral domains

Monolithic Solid-State Lasers for Spaceflight

A new solution for building high power, solid state lasers for space flight is to fabricate the whole laser resonator in a single (monolithic) structure or alternatively to build a contiguous diffusion bonded or welded structure. Monolithic lasers provide numerous advantages for space flight solid state lasers by minimizing misalignment concerns. The closed cavity is immune to contamination. The number of components is minimized thus increasing reliability. Bragg mirrors serve as the high reflector and output coupler thus minimizing optical coatings and coating damage. The Bragg mirrors also provide spectral and spatial mode selection for high fidelity. The monolithic structure allows short cavities resulting in short pulses. Passive saturable absorber Q-switches provide soft aerturing fro spatial mode filtering and improved pointing stability. We will review our recent commercial and in-house developments toward fully monolithic solid state lasers

Determination Of Composition Of Photo-Thermo-Refractive Glass By Sims

The secondary ion mass spectrometry (SIMS) analytical technique is optimised for relative composition measurements of photo-thermo-refractive (PTR) glass, which is a photosensitive glass for volume hologram recording. The elemental depth distribution was measured for virgin and thermally developed PTR glass. It is found that main photosensitive components have nonuniform profiles of concentration which resulted from exposure and thermal development. A novel SIMS metrology is developed for discrimination of halide ions incorporated in vitreous and crystalline phases

Radiation-Induced Absorption In A Photo-Thermo-Refractive Glass

Photo-thermo-refractive (PTR) glass is a new photosensitive material for phase hologram recording. This sodium-zinc-aluminum-silicate glass doped with silver, cerium and fluorine exhibits a refractive index modulation after exposure to UV radiation followed by a thermal treatment. Holographic volume gratings recorded in this glass show an absolute diffraction efficiency exceeding 97%, a thermal stability up to 400°C, and a high tolerance to laser radiation. These features support its application for laser beam control in optical communications and surveillance in space-born systems. A specific aspect of the space environment is the presence of ionizing radiation, which is known to influence the properties of optical materials. We studied the induced absorption in PTR glass after exposure to gamma radiation with doses exceeding 10 Mrad. The larger part of the induced absorption is found in the visible and UV spectral regions while in the infrared the absorption level remains sufficiently low to allow a long-term use of this material in space. In this paper, we discuss the structure of the induced absorption spectra in PTR glass and glass matrix which does not contain photosensitive agents

Luminescence Of Dopants In Ptr Glass

Photo-thermo-refractive (PTR) glass is a silica sodium aluminium zinc glass containing oxygen and fluorine as anions and four dopants, such as Ce, Ag, Sb and Sn, in which concentrations vary in the range of 0-1-0-01%. The main photochemical reaction occurring during the hologram recording (UV irradiation) is an electron transfer from Ce3+ to Ag+, which results information of Ag containing particles. Further thermal development causes the growth of NaF crystals on Ag particles. The main goal of this work was to elaborate the method of the luminescence analysis of PTR glass, and to find and identify the excitation and emission spectra of each dopant in PTR glass. All four dopants have excitation and emission spectra overlapping each other. In order to separate them, seven melts of PTR glass matrix without any dopants and with one or two dopants have been made. Each dopant has been added in the same concentration as it appears in a regular PTR glass. It was found that luminescence of Ce3+ has the highest intensity and masks the other dopants, except one of Sb3+. This work enables the further study of the behaviour of dopants in PTR glass matrix on each step of hologram writing

Refractive Index Modulation In Photo-Thermo-Refractive Fibers

Refractive index decrement was discovered in a fiber made from photo-thermo-refractive (PTR) glass. PTR glass is a fluorosilicate glass doped with cerium and silver which demonstrates refractive index change after UV exposure and thermal development due to precipitation of NaF nanocrystals in the irradiated areas. This glass is widely used for volume holographic optical elements recording. Photosensitivity in PTR optical fibers has been shown after exposure to radiation at 325 nm for about 1 J/cm 2 followed by thermal development at 520°C. Refractive index difference between exposed and unexposed areas was about 1000 ppm. A Bragg mirror at 1088 nm was recorded in such fiber which showed narrow band reflection within 1 nm