A self-scanned 1024 element photodiode array and minicomputer are used to measure the phase (wavefront) in the interference pattern of an interferometer to lambda/100. The photodiode array samples intensities over a 32 x 32 matrix in the interference pattern as the length of the reference arm is varied piezoelectrically. Using these data the minicomputer synchronously detects the phase at each of the 1024 points by a Fourier series method and displays the wavefront in contour and perspective plot on a storage oscilloscope in less than 1 min (Bruning et al. Paper WE16, OSA Annual Meeting, Oct. 1972). The array of intensities is sampled and averaged many times in a random fashion so that the effects of air turbulence, vibrations, and thermal drifts are minimized. Very significant is the fact that wavefront errors in the interferometer are easily determined and may be automatically subtracted from current or subsequent wavefrots. Various programs supporting the measurement system include software for determining the aperture boundary, sum and difference of wavefronts, removal or insertion of tilt and focus errors, and routines for spatial manipulation of wavefronts. FFT programs transform wavefront data into point spread function and modulus and phase of the optical transfer function of lenses. Display programs plot these functions in contour and perspective. The system has been designed to optimize the collection of data to give higher than usual accuracy in measuring the individual elements and final performance of assembled diffraction limited optical systems, and furthermore, the short loop time of a few minutes makes the system an attractive alternative to constraints imposed by test glasses in the optical shop.

Digital wavefront measuring interferometer for testing optical surfaces and lenses

A description is given of the research progress in developing a vertical-cavity surface-emitting (SE) injection laser based on GaAlAs/GaAs and GaInAsP/InP systems Ultimate laser characteristics, device design, state-of-the-art performances, possible device improvement, and future prospects will also be discussed The authors propose a vertical-cavity surface emitting semiconductor laser To reduce the threshold current, they improved the laser reflector and introduced a circular buried heterostructure The microcavity structure, which is 7 mu m long and 6 mu m in diameter, was realized with a threshold of 6 mA Thus, possibilities of an extremely low threshold current SE laser device and a densely packed two-dimensional array are suggested >

Surface emitting semiconductor lasers

A microlens fabrication process is described which can be used in applications requiring integration of optical elements (lenses) and microcircuits. The process is fully compatible with IC fabrication technology and uses commercially available IC processing materials. The obtained microlenses are of excellent quality and basically show diffraction-limited resolution with ~1-μm spot size. Extensions of the process to production of nonspherical lenses and use of alternative material packages are also discussed.

Technique for monolithic fabrication of microlens arrays

The invention provides a laser beam machining method characterized by comprising the steps of mounting a protective tape (25) on the surface (3) of a wafer (1a), radiating laser light (L) by using the back (21) of a wafer (1a) as a laser light incidence plane with an optical converging point (P) positioned in a substrate (15) to thereby form a melt processing region (13) for melt processing by multiphoton absorption, forming, by means of the melt processing region (13), a cutting start region (8) on the side within a predetermined distance from the laser light incidence plane along a predetermined cutting line (5) on the wafer (1a), mounting an expand tape (23) on the back (21) of the wafer (1a), and stretching the expand tape (23) to thereby separate a plurality of chip-like portions (24) from each other that are formed by the wafer (1a) being cut with the cutting start region (8) used as the starting point.

Laser beam machining method

A stacked array magnifier (SAM) forms a magnified, demagnified or unit image of an object. The SAM includes one or more non-refractive lenslet arrays and one or more refractive lenslet arrays to form a plurality of lenslet channels. Each lenslet channel has at least one refractive lenslet and at least one non-refractive lenslet. SAMs are combined and tiled to form a scaleable display of flat panel displays. Multiple SAMs are used to increase magnification selectively. Hybrid lenslet arrays of the invention are also useable for optical processing and non-imaging applications.

Lenslet array systems and methods

In this paper we present a new development of the distributed-index planar microlens of 2.5-3-mm focal length and 0.15 N.A. and also show that it is usable with optical components in fiber communications. We then propose a concept of stacked planar optics consisting of a stack of arrayed planar microlenses and other optical components. From this configuration a 2-D array of optical devices is monolithically available, and many discrete components can be separated from the array. An optical tap array has been fabricated as an example of stacked planar optics.

Stacked planar optics: an application of the planar microlens

Planar technology has been used to make a microlens array monolithically. By selectively diffusing a dopant into the planar substrate a distributed-index planar microlens has been realized. The monomer exchange technique for the plastic substrate and ion exchange and electromigration techniques for the glass substrate are used. In particular a 2-D planar microlens array was fabricated in a glass substrate. Each microlens was 1.2 mm in diameter and the focal length was 9.4 mm. The focused spot of the collimated He-Ne laser beam was as small as 17 micromphi.

Distributed-index planar microlens

A new class of arrayed distributed-index planar micro-lenses on a planar glass substrate has been monolithically fabricated. Each lens is with 1.2 mm in diameter and measured focal length is 9.4 mm. The minimum light spot which has been focused by the lens is as small as 17 µm which is almost limited by the diffraction. Clear images have been formed with a 5×5 lens array.

https://iopscience.iop.org/article/10.1143/JJAP.20.L296/pdf

Array of Distributed-Index Planar Micro-Lenses Prepared from Ion Exchange Technique

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.

Masahiro Oikawa

Papers

Stacked planar optics: an application of the planar microlens

Distributed-index planar microlens

Array of Distributed-Index Planar Micro-Lenses Prepared from Ion Exchange Technique

Multiple imaging and multiple Fourier transformation using planar microlens arrays

Fundamentals of microoptics