R. R. Stephens

An electro‐optic tunable filter

This letter describes a tunable optical filter that couples light energy between ordinary and extraordinary polarizations in a birefringent electro‐optic crystal at the phase‐matched wavelength by means of a spatially periodic dc electric field. The specific embodiment described here is a LiTaO3 platelet operating with transverse electric field and located between cross polarizers. Analogies to both the Solc birefringent filter and the Harris acousto‐optic filter are cited. The electro‐optic filter is tuned by varying the spatial period of the electric field via an array of separately addressable finger electrodes. We have demonstrated tunability from 4700 A to 4.5 μm. Experimental results of transmittance versus applied voltage and of bandwidth versus pass wavelength agree well with theory. The flexibility of this type of electronic filter in allowing synthesis of arbitrary transfer functions through nonperiodic voltage distributions is emphasized.

Diode-pumped upconversion laser with 100-mW output power

A high-power semiconductor diode-laser array operating at 797 nm has been used to pump an Er:YLiF(4) upconversion laser with output at 551 nm operating at 48 K. By carefully controlling the beam geometry and oscillating linewidth of the diode-pumped laser, it has been possible to obtain 100 mW of visible output power with a conversion efficiency from the IR to the visible of greater than 5%.

Efficient self-pumped phase conjugation at near-infrared wavelengths using cobalt-doped BaTiO(3).

Using BaTiO(3) crystals doped with cobalt, we have measured the reflectivity of self-pumped phase-conjugate mirrors operating in the total-internal-reflection geometry as a function of wavelength in the range between 633 and 933 nm. We find that for cobalt concentrations above 25 parts in 10(6), the reflectivity is higher than 50% for all the investigated wavelengths. At a wavelength of 800 nm the reflectivity is independent of incident power over a range of 12 to 600 mW.

Phase conjugate master oscillator‐power amplifier using BaTiO3 and AlGaAs semiconductor diode lasers

A double pass phase conjugate master oscillator‐power amplifier has been demonstrated at 820 nm using AlGaAs gain elements and BaTiO3 in a self‐pumped ring configuration. Single frequency operation with diffraction‐limited output beam quality was achieved at output powers in excess of 50 mW cw.

Experimental study of an adaptive-laser resonator

Correction of static-resonator misalignment errors in a CO2 laser has been obtained through the use of an intracavity deformable-mirror adaptive-optical system. Correction of the near-field intensity distribution has been observed, accompanied by total-power increases of a factor of 2. Restoration of the far-field beam quality has been demonstrated, yielding far-field peak-intensity increases of a factor of 11.

A multilayer AgGaS2 structure for infrared (2-10 μm) electro-optic tunable filters: fabrication and performance

Alternating layers of high‐ and low‐resistivity silver thiogallate (AgGaS2) were grown sequentially by liquid‐phase epitaxy on AgGaS2 substrates using the vertical dipping technique. High‐resistivity layers were grown by using KCl‐AgGaS2 solutions while low‐resistivity layers were grown from Ge‐AgGaS2‐KCl solutions. Layer growth of such a multilayer device and demonstration of its electro‐optic response for filter application are described.

Harmonic response of a tunable Solc filter

The spectral evolution and transitional behavior of the odd harmonic windows in a broadly tuned electrooptic Solc filter are described theoretically and demonstrated experimentally. We show how the fundamental and all the odd harmonic passbands split and eventually merge in pairs with nearest neighbors to become even harmonics of the fundamental λf as the principal pass wavelength λp is tuned from λp = λf to λp ≫λf.

Programmable Electro-Optic Tunable Filters

An optical filter has been developed in which the operating wavelength, linewidth, line shape and peak transmission can be independently controlled. In this filter, the optical interaction is controlled electro-optically thereby requiring much less drive power than similar filters using the acousto-optic interaction. A filter has been fabricated and tuned through the visible portion of the spectrum. The programming features of the filter are described in this paper.