Results for a new compact 488 nm solid-state laser for biomedical applications are presented. The architecture is based
on a multi-longitudinal mode external cavity semiconductor laser with frequency doubling in a ridge waveguide fabricated in periodically poled MgO:LiNbO3. The diode and the waveguide packaging have been leveraged from telecom packaging technologies. This design enables built-in control electronics, low power consumption (≤ 2.5 W) and a footprint as small as 12.5 x 7 cm. Due to its fiber-based architecture, the laser has excellent beam quality, M2 <1.1. The laser is designed to enable two light delivery options: free-space and true fiber delivered output. Multi-longitudinal
mode operation and external doubling provide several advantages like low noise, internal modulation over a broad frequency range and variable output power. Current designs provide an output power of 20 mW, but laser has potential for higher power output.
Computer-generated holograms are limited by conventional lithographic fabrication capabilities which rely on accurate deposition, exposure, and developing of photosensitive chemicals. We present an alternate fabrication technology that uses a focused laser beam to write patterns by inducing a thermochemical change in a bare metal film. The patterns are developed using a single etching step that dissolves the non- exposed metal. The thermochemical writing method allows holograms to be directly written onto large-diameter, thick, and non-flat substrates, requiring no intermediate steps that compromise the ultimate accuracy. Circular patterns for optical testing were written using a polar-coordinate laser writer. The laser power and control requirements are shown to be modest and the etching is shown to be tolerant of temperature and concentration variations. The technology is demonstrated with the fabrication of CGHs up to 136 mm in diameter used for optical testing.
An optical beam shaping system based on a single Computer Generated Hologram has been realized. It focuses a laser beam with Gaussian profile to a square area with uniform intensity. In order to achieve a rectangular focal spot which is as close as possible to the size of the diffraction spot, we investigated two different hologram calculation methods. The first is based on a ray tracing approach, while the second one uses an iterative Fourier transform algorithm. Computer simulations and experimental results are shown.
The hybrid micro-objective lens with the kinoform corrector has been developed and fabricated. Kinoform corrector is made by the photorastering technology. The numerical aperture of the micro-objective is 0.6 and 0.7; the focal length is 9.1 and 5.9 mm. The micro- objective can find its applications for various laser interferometers to collimate radiation of diode lasers and for date recording and read-out optical and magneto-optical disks.