A new type of multiple imaging and multiple Fourier transformation system under coherent illumination using microlens arrays has been developed. The optical system is based on geometrical optics instead of convolution or diffraction. As a result, it has the advantage of design flexibility especially in alignment of the duplicate images. The experimental results of the system, which are implemented using planar microlens arrays fabricated by an ion exchange technique, are also discussed.
We demonstrate pulse laser operation of a Pr:LiYF(4) laser pumped by InGaN laser diodes (444 nm) using an acousto-optic modulator. We obtained a maximum laser peak power of 167 W (4 μJ/pulse) with a pulse width of 24 ns at an 11 kHz repetition rate for a 63 nm wavelength. Employing an 8 mm long lithium triborate nonlinear crystal in the laser cavity, we obtained a maximum peak power of 55 W (2.7 μJ/pulse) at 320 nm, which corresponds to a conversion efficiency of 69% with respect to the fundamental laser energy. The UV laser pulse width was 36 ns.
The planar microlens is a 2-D integrated microlens fabricated by the selective ion exchange technique. This paper demonstrates a new class of planar microlens which has a high numerical aperture. The new planar microlens uses a swelling structure and index distribution which comes from replacing ions with different ion volumes. Lens diameters from 10 to 400 microm can be fabricated. A numerical aperture larger than 0.5 is achieved when the lens diameter is smaller than 100 microm. Use of this microlens in light coupling between an LD and a single-mode fiber is also evaluated.
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