Wd. Cowan et al., Optical phase modulation using a refractive lenslet array and microelectromechanical deformable mirror, OPT ENG, 37(12), 1998, pp. 3237-3247
Microelectromechanical deformable mirrors (MEM-DMs) are attractive for opti
cal phase modulation applications primarily because of their inherently low
cost and low drive voltages. Two problems limiting widespread use of segme
nted piston MEM-DMs are low optical efficiency (fill factor) and undesired
amplitude modulation resulting from interference with the static background
structure. Using a lenslet array to focus the incident light onto only the
reflective surface of the MEM-DM greatly improves the effective fill facto
r with a corresponding decrease in interference effects. A refractive lensl
et array is used with a very low fill factor MEM-DM (similar to 7%) to comp
rise a correcting element that behaves like a 70 to 80% fill factor device.
The MEM-DM has 128 active piston micromirror elements. Experiments employi
ng the hybrid correcting element demonstrate single beam steering, dual bea
m steering, and optical aberration correction. A comprehensive model of the
lenslet/MEM-DM geometry is developed. Measured data shows goad agreement w
ith model predictions. A thermal circuit model is developed to estimate opt
ical power handling capability of the MEM-DM. A conservative estimate of ma
ximum optical power for this particular MEM-DM is 4 W/element when operated
in a helium ambient, suggesting that relatively high power laser control a
pplications are feasible, (C) 1998 Society of Photo-Optical Instrumentation
Engineers. [S0091-3286(98)01812-1].