Improved sensitivity in blue-membrane bacteriorhodopsin films.

We show that D85N/V49A, a mutant bacteriorhodopsin in which two residues, aspartate (D) at position 85 and valine (V) at position 49, have been replaced with asparagine (N) and alanine (A), respectively, has significantly improved optical properties compared with other forms of blue-membrane Bacteriorhodopsin. Absorption studies of the mutant in gels show that it forms the P(490) state at light levels that are comparable with M-state formation in wild-type films. Theoretical calculations based on Kramers-Kronig transformation of light-induced absorption data predict that the refractive index is three times larger than that of mutant D85N. Holographic measurements performed on gelatin-based films confirm that the sensitivity is improved by a factor of 50 over that of D85N.

Holographic profilometry with a rhodium-doped barium titanate crystal and a diode laser.

We present a novel, whole-field, noncontact profilometer based on real-time, two-color contour holography. A single 30-mW laser diode was used to record a hologram in a BaTiO(3):Rh crystal, and the reconstructed image was interfered with the real-time object wave. Current modulation of the diode laser produced continuously tunable contour intervals. The resulting interferograms were processed by use of phase-shift interferometry algorithms to yield quantitative, three-dimensional measurements of the original object. We demonstrate submillimeter depth resolution and show how resolution and speed can be further improved.

Resonant holographic interferometry with ZnTe:V:Mn.

The photorefractive semiconductor ZnTe:V:Mn is investigated for use in real-time resonant holographic interferometry applications. Experimental results of two-wave and four-wave mixing with pulsed dye and cw diode lasers are presented; in addition holographic image transfer, as well as two-wavelength resonant holographic interferometry, are demonstrated. Species-specific interferograms of potassium seeded into various combustion environments are captured at video-frame rates. Calculations of the species measurement sensitivity and dynamic range are presented, and design considerations for resonant holographic interferometry systems employing photorefractive materials are outlined.

Real-time resonant holography using bacteriorhodopsin thin films.

We demonstrate real-time, two-dimensional measurement of species concentration in a turbulent flow field. The dynamics of pulsed holographic recording and decay are characterized for a 46-microm polymer film containing bacteriorhodopsin. We produced species-specific holographic interferograms of sodium vapor by simultaneously recording two holograms at different wavelengths, one tuned near a sodium absorption feature and the other tuned off resonance. An analysis of the techniques' sensitivity is presented.

Room-temperature 1.06-0.53-microm second-harmonic generation with MgO:LiNbO(3).

Room-temperature 1.06-0.53-microm second-harmonic generation (SHG) achieved with LiNbO(3) doped with 7 mol. % MgO has been studied. Phase matching was achieved with angle tuning. SHG conversion efficiency of 45% was obtained with a 12-mm-long crystal and a fundamental peak-power density of 140 MW/cm (2). SHG performance of MgO:LiNbO(3) is compared with that of KTP and LBO crystals. Various phase-matching parameters of MgO:LiNbO(3) were calculated as functions of the fundamental wavelength, using the experimentally determined Sellmeier equations. It was found that room-temperature, noncritically-phase-matched Type I SHG can be achieved in this crystal at 1.053 microm, where Nd:YLF lasers operate.