Organic materials exhibiting strong two-photon absorption cross-sections and subsequent up-converted fluorescence have been targeted for use in a variety of applications including optical data storage, nondestructive imaging, frequency up-converted lasing, and microfabrication. In order for these materials to be useful in practical application they must either be coupled with a liquid solvent or doped into a solid host material. The purpose of this study is to examine effects of different host environments on the nonlinear photophysical properties of AF-455, a recently developed organic two-photon absorber. We present results of experiments using both emission and absorption methods to characterize the linear and nonlinear response of AF-455 dissolved in solvents of varying polarity and doped in a polymer (PMMA) matrix.

The formation of a Graded Index of Refraction (GRIN) lens is possible by using two-photon induced polymerization. Preliminary GRIN profiles are presented with a short discussion on application to deformable lenses.

A cascade of microlens arrays that are decentered with respect to each other is one potential method for beam steering; the magnitude of the steering angle depends on the amount of decenter. A simple argument is presented that shows that the output of such a system is analogous to the output of an optical phased array. The periodic nature of the exiting wavefront restricts allowed steering angles to values that are determined by the grating equation and the pitch of the microlens arrays. The efficiency of steering into a desired diffraction order of the phased array is determined by the amount of decenter of the microlens arrays, the coherence of the arrays, and the fill-factor at the output of the array. Maximum fill-factor is desired, which can be achieved through the addition of an intermediate microlens array that acts like a field lens. An experimental implementation of such a triplet cascade of microlens arrays, suitable for steering short wave infrared laser light, is described. The extension of such a cascade to steering broad spectral band light is also discussed.

"Active" sensors (systems that employ lasers as an illumination source) have several advantages. In particular, multiple phenomenologies can be measured. This paper describes the types of measurements possible and the required source and receiver components.

We present four receiver designs for a ladar system, based on an optical parametric amplifier, that is designed to collect returns from glint targets. After coupling the return energy into periodically poled lithium niobate, the target backscatter is detected with either an infrared camera or a CCD array. Assuming reasonable detector and system characteristics, the sensitivity of each design is then evaluated by setting the receiver SNR detection threshold equal to one and using the minimum transmitted energy as the figure of merit. Through numerical analysis, we show that an upconversion receiver followed by a visible CCD array offers the best trade-off between sensitivity and practical design for airborne ladar applications.

We investigate the space-bandwidth product of a ladar system incorporating an upconversion receiver. After illuminating a target with an eye-safe beam, we direct the return into a piece of periodically poled LiNbO3 where it is upconverted into the visible spectrum and detected with a CCD camera. The theoretical and experimental transfer functions are then found. We show that the angular acceptance of the upconversion process severely limits the receiver field of regard for macroscopic coupling optics. This limitation is overcome with a pair of microlens arrays, and a 43% increase in the system's measured space-bandwidth product is demonstrated.

The return signal frequency of an eye-safe ladar system is upconverted from the infrared to the visible through sum-frequency generation by incorporation of periodically poled LiNbO3 into the receiver. A quantitative analysis of the angular acceptance and the quantum efficiency is then presented for a single macroscopic receiver optic and a multiaperture microlens array. Comparing both results, a 6x increase in the receiver field of regard and an 18% increase in beam coupling were realized for the microlens design over the macroscopic system.

A rigorous method for modeling received power coupling efficiency (ηF/R) and transmitted power coupling efficiency (ηF/T) in a general-target-illumination ladar system is presented. For our analysis we concentrate on incorporating a single-mode optical fiber into the ladar return signal path. By developing expressions for both ηF/R and ηF/T for a simple, diffuse target, our model allows for varying range, beam size on target, target diameter, and coupling optics. Through numerical analysis ηF/R is shown to increase as the range to target increases and decrease as target diameter increases, and ηF/T is shown to decrease with target range. A baseline signal-to-noise ratio analysis of the system is also provided for varying illumination schemes.