Combining and collimation of RGB laser beams with transmissive resonance domain diffractive optics.

Resonance domain diffractive optical elements for combining RGB laser beams into a single collimated beam were designed, fabricated, and experimentally investigated. The input RGB beams were angular separated up to tens of degrees and set in a nearly Bragg arrangement for high diffraction efficiency. A single resonance domain diffractive lens delivered beam combining and collimation functions with reasonable residue divergence. The resonance domain diffraction grating delivered diffraction-limited residue divergence in combining the collimated RGB beams. Optical experiments with fiber-coupled RGB lasers and e-beam-fabricated beam combiners proved low residue beam divergence, a high polarization extinction ratio, and total measured diffraction efficiency of about 80%.

Resonance-domain diffractive microlens arrays.

High-efficiency resonance-domain diffractive microlens arrays with high numerical apertures and 100% fill factor were designed, fabricated, and characterized. Fabricated arrays of eight off-axis microlenses with pitch 127 µm and numerical aperture 0.2 demonstrated diffraction-limited collimation of fiber light at 632.8 nm wavelength. Optical measurements revealed diffraction efficiency exceeding 93%, in match to numerical calculations with rigorous conical diffraction. The resonance-domain diffractive microlens arrays are highly suitable for applications in fiber optics, multispot optical tweezers, optical sensors, and spectrometry.

Multifunctional binary diffractive optical elements for structured light projectors.

A set of diffractive optical elements for multiple-stripe structured illumination was designed, fabricated and characterized. Each of these elements with a single layer of binary surface relief combines functions of a diffractive lens, Gaussian-to-tophat beam shaper, and Dammann beam splitter. The optical investigations of laser light patterns at 20° fanout angle reveal up to 88% diffraction efficiency, high contrast, and nearly diffraction limited resolution. The developed technology has the potential for reducing complexity, number of optical components, power consumption and costs of structured light projectors in mobile and stationary 3D sensors.

Coherent imaging with a resonance domain diffractive lens in laser light.

We investigated coherent imaging with a binary off-axis resonance domain diffractive lens using three lasers in visible wavelengths. The relations between the dispersion of this lens, shape of its point spread function, and spectral properties of these lasers were analyzed theoretically and experimentally. In particular, we measured the point spread function, imaging contrast, and diffraction efficiency. Experimental results proved the feasibility of imaging with low distortion and more than 83% diffraction efficiency in laser light.

Chromatic dispersion of a high-efficiency resonance domain diffractive lens.

Inherent strong lateral and longitudinal chromatic dispersion of a transmission resonance domain off-axis diffractive lens were studied theoretically and experimentally. It is shown that a 4 mm diameter and 0.14 NA diffractive lens provides both focusing and dispersion with a spectral resolution of up to 0.09 nm, which is suitable for laser line spectral measurements. Experimental results for measured spectra of a mercury-argon source, a helium-neon laser, and RGB laser diodes pave a technological path to compact spectral sensors and microspectrometers.

Resonance domain surface relief diffractive lens for the visible spectral region.

Early expectations for a role of diffractive lenses were dramatically lessened by their high order overlapping foci, low optical powers, and competing advances in refractive micro-optics. By bringing the Bragg properties of volume holograms to diffractive lenses we got rid of ghost diffractive orders and the critical trade-off between diffraction efficiency, number of phase levels, and spatial feature-size. Binary off-axis resonance domain diffractive lens with high numerical aperture of 0.16 was designed with analytical effective grating theory, fabricated by direct e-beam writing, etched in fused silica and experimentally investigated. More than 81% measured diffraction efficiency exceeds twice the limits of thin binary optics.

Design and experimental investigation of highly efficient resonance-domain diffraction gratings in the visible spectral region.

Surface-relief resonance-domain diffraction gratings with deep and dense grooves provide considerable changes in light propagation direction, wavefront curvature, and nearly 100% Bragg diffraction efficiency usually attributed only to volume optical holograms. In this paper, we present design, computer simulation, fabrication, and experimental results of binary resonance-domain diffraction gratings in the visible spectral region. Performance of imperfectly fabricated diffraction groove profiles was optimized by controlling the DC and the depth of the grooves. Indeed, more than 97% absolute Bragg diffraction efficiency was measured at the 635 nm wavelength with binary gratings having periods of 520 nm and groove depths of about 1000 nm, fabricated by direct electron-beam lithography and reactive ion etching.

Airy beam laser.

A method to design lasers that emit an arbitrary beam profile is studied. In these lasers, output-coupling is performed by a diffraction grating that imposes a phase and amplitude distribution onto the diffracted light. A solid-state laser emitting beams with a two-dimensional Airy intensity profile is demonstrated both theoretically and experimentally. In this case, the diffraction grating adds a transverse cubic phase to the diffracted light. An Airy beam is obtained by performing optical Fourier transform of the out-coupled light. The laser beam profile and power characteristics are shown to agree with theory.