A.A. Gorokhovsky

Spectral hole burning in naphthalocyanines derivatives in the region 800 nm for holographic storage applications

Persistent spectral hole burning is studied for several free-based and metallo-naphthalocyanine derivatives in polymer hosts. These materials exhibit a strong 0-0 absorption band in the region 800 nm matching the wavelength range of most semiconductor diode lasers and Ti:Sapphire lasers. Metallo-naphthalocyanines demonstrate a nonphotochemical hole-burning mechanism that is likely related to rotations of small molecular groups attached to a relatively rigid molecular ring. Free-base molecules exhibit the regular proton phototautomerization mechanism of hole burning. Spectral- and hole-burning parameters were determined for eight materials; in particular, the hole-burning kinetics was analyzed and the quantum efficiencies were determined to be between 0.1% and 1%. Holograms (data pages) in the transmission geometry were successfully recorded in the materials studied using single-frequency laser diodes.

Photoluminescence spectra of xenon implanted natural diamonds

The natural diamonds were implanted with 500 keV Xe ions within the dose range 1 x 10 13 -5 x 10 14 cm- 2 . The post-implantation thermal annealing was carried out gradually at temperatures between 300°C and 1400°C. Photoluminescence spectra were measured after each annealing step in the temperature range 1.5-200K. The spectra featured the Xe-related zero phonon line (ZPL) at 811.6 nm (1.527eV) and a vibronic sideband with several quasilocal and phonon peaks. The Huang-Rhys factor was determined to be exp (-S) =0.5 ± 0. 1. The ZPL at 1.5 K is is inhomogeneously broadened and has line width in the range 5.5-15 cm -1 depending on the implantation dose. It was concluded that the vacancy is involved in the Xe center formation. The photoluminescence is significantly quenched by the irradiation-induced defects. A growth of the second ZPL at 793.3 nm was observed at elevated temperatures. The excited state energy level splitting of △E= 128±20cm -l was found by studying the temperature behavior of these ZPLs. It was concluded that the excited state, as well as the ground state of the optical transition, has a double level structure, and that ZPL at 811.6 is not, likely, a resonance 0-0 line.

Determination of quantum efficiency of persistent spectral hole burning using dispersive kinetics

Abstract A practical approach for the determination of the quantum efficiency of persistent spectral hole burning (PSHB) is suggested. The quantum efficiency is found from the experimental kinetics of hole formation. The method takes into account all primary mechanisms of dispersion for the hole burning kinetics and can be applied to the characterization and the comparison of materials with different mechanisms of hole burning. The quantum efficiency of PSHB has been found for free-base and zinc naphthalocyanines, which have photochemical and photophysical mechanisms of PSHB, respectively. These materials are useful for PSHB applications in the spectral range around 800 nm.

Spectroscopy and micro-luminescence mapping of Xe-implanted defects in diamond

Ion implantation in diamond creates optically active defects which have emission lines in broad spectral regions and may be used in advanced photonics and optical communication applications. A brief review of the photoluminescence properties of Xe+ ion implanted diamond is presented. The Xe-related center is of particular interest as this center is one of a few centers (Ni, Si, Cr) in diamond having sharp emission lines in the infrared spectral region, specifically at 813 and 794nm. The paper discusses an approach to determine the important and difficult to measure conversion efficiency of implanted ions into emitting optical centers. The method uses micro-luminescence confocal mapping and statistical analysis based on a compound Poisson distribution, accounting for both the implanted centers and the optically excited centers statistics. Results of numerical simulations and experimental measurements are presented.

Spectroscopy, persistent hole burning, and holographic applications of naphtophthalocyanine/haloanthracene systems

We report on the spectroscopic and hole burning properties of free-base naphtophthalocyanine with and without 1-chloranthracene in polymer host. These materials exhibit a strong 0-0 absorption band in the region 800 nm matching the wavelength range of most semiconductor and Ti:Sapphire lasers. The materials studied feature two persistent hole burning photochemical mechanisms, i.e. one-photon proton tautomerization, and two-photon-gated hole burning likely due to donor-acceptor electron transfer. The last mechanism includes the long living intermediate state. The hole width at 1.5 K is about 300-400 MHz depending on the hole burning conditions, while the inhomogeneous width is about 107 MHz. Holographic storage is an important potential application of these materials. We demonstrated 10 plane wave holograms angularly multiplexed at one frequency channel in a spectral hole burning medium. It was shown that the M/# is still a valid system metric and the measured M/# in one frequency channel is about 0.01.

Optical spectroscopy of Tm3+ in organic matrices for hole-burning storage applications

The optical properties of four Tm3+ chelates, specifically (beta) -diketone tris chelates of thulium, in a poly(methyl methacrylate) matrix are presented. Samples under investigation were the Tm3+ complexes formed using thulium chloride (TmCl3 (DOT) 6H2O) with thenoyltrifluoroacetylacetone (TTFA), 1,1,1-trifluoro-2,4- pentanedione (TFD), 1-phenyl-1,3-butanedione (PBD), and 1,3- diphenyl-1,3-propanedione (DBM) ligands. These materials are interesting from the point of view of potential applications for optical hole-burning frequency and time-domain storage and processing. Optical absorption, steady state and time-resolved photoluminescence, and spectral hole-burning at the transition between 3H6(1) and 3H4(1) crystal-field levels were studied at temperatures between 1.4 and 300 K.

Organic materials for spectral hole burning and non-hole burning optical filters

A brief overview of spectral properties and applications of organic materials for narrowband persistent spectral hole burning (SHB) and non-hole burning optical spectral filters is presented. The main focus is on the properties important for the filter applications in ultrasound-modulated optical tomography (UOT). Due to the large inhomogeneous broadening, the organic SHB filters may be used after the more narrowband primary SHB filters made of RE ion doped inorganic crystals to reduce red-shifted fluorescence from RE ions and improve the image quality. In addition non-hole burning organic materials, as secondary absorption optical filters to reduce phonon-mediated fluorescence from inorganic SHB crystals in UOT applications, are considered.

Derivation and measurement of the M/# in spectral hole burning media

We demonstrate 10 plane wave holograms angularly multiplexed at one frequency channel in spectral hole burning medium. We show that the M/# is still a valid system metric and the measured M/# in one frequency channel is about 0.01.

Multiplexing and M# measurement in spectral hole burning medium

Summary form only given Spectral hole burning holography can store both the temporal and spatial information. In cryogenic temperature, only a certain group of atoms in the spectral hole burning material can interact with the incident photons of specific frequency. It allows an extra degree of freedom to store and access information, i.e. the frequency domain. 12,000 holograms at a single location by frequency multiplexing has been demonstrated. The storage capacity can be further increased by combining angle and frequency multiplexing. A system measure of the hologram diffraction efficiency obtainable by multiplexing M holograms at a single location and frequency is given by the M/#. In the paper we report the measurement of M/# in a 400 /spl mu/m thick sample of H/sub 2/TBNP in polyvinyl butyral (PVB) with a concentration of 3 /spl times/ 10/sup -5/ mol/l.

Evaluation of vibration generated by closed-cycle refrigeration system using optical methods

A simple optical method for studying vibration has been developed and applied to the investigation of a commercial closed cycle refrigeration (CCR) system. This method utilizes an amplitude modulation of a laser beam by the knife-edge attached to the cold finger of the CCR system. The sensitivity of the proposed optical technique is determined by the diameter of the focused laser beam and a displacement of 1 micrometers is readily detectable. For the system CRYO Model 396-022 based on CTI CRYODYNE Model 22 refrigerator, experimental studies were conducted for different cold finger temperatures, cold head orientations, and mechanical holders. The total amplitude of the displacement was on the order of 50 micrometers for a cold head fixed into rigid mechanical holder placed on the optical table and 30 micrometers for the same holder placed on a special stand decoupled from the optical table. Three main frequency components at 3 Hz, 60 Hz, and 120 Hz have been observed.