Adaptive beam shaping by controlled thermal lensing in optical elements.

We describe an adaptive optical system for use as a tunable focusing element. The system provides adaptive beam shaping via controlled thermal lensing in the optical elements. The system is agile, remotely controllable, touch free, and vacuum compatible; it offers a wide dynamic range, aberration-free focal length tuning, and can provide both positive and negative lensing effects. Focusing is obtained through dynamic heating of an optical element by an external pump beam. The system is especially suitable for use in interferometric gravitational wave interferometers employing high laser power, allowing for in situ control of the laser modal properties and compensation for thermal lensing of the primary laser. Using CO(2) laser heating of fused-silica substrates, we demonstrate a focal length variable from infinity to 4.0 m, with a slope of 0.082 diopter/W of absorbed heat. For on-axis operation, no higher-order modes are introduced by the adaptive optical element. Theoretical modeling of the induced optical path change and predicted thermal lens agrees well with measurement.

[1]  G. Mueller,et al.  Adaptive control of laser modal properties. , 2006, Optics letters.

[2]  P. Fritschel,et al.  Active correction of thermal lensing through external radiative thermal actuation. , 2004, Optics letters.

[3]  A.K. Poteomkin,et al.  Compensation of thermally induced modal distortions in Faraday isolators , 2004, IEEE Journal of Quantum Electronics.

[4]  D. Blair,et al.  Thermal lensing compensation for AIGO high optical power test facility , 2004 .

[5]  Alan J. Weinstein,et al.  Advanced LIGO optical configuration and prototyping effort , 2002 .

[6]  M. Fejer,et al.  Model of thermal wavefront distortion in interferometric gravitational-wave detectors . I . Thermal focusing , 2002 .

[7]  P. Fritschel,et al.  Adaptive thermal compensation of test masses in advanced LIGO , 2001, gr-qc/0110011.

[8]  M. Fejer,et al.  Evaluating the effect of transmissive optic thermal lensing on laser beam quality with a shack-hartmann wave-front sensor. , 2001, Applied optics.

[9]  A. Rüdiger,et al.  Thermal lensing in recycling interferometric gravitational wave detectors , 1994 .

[10]  Winkler,et al.  Heating by optical absorption and the performance of interferometric gravitational-wave detectors. , 1991, Physical review. A, Atomic, molecular, and optical physics.

[11]  Patrice Hello,et al.  Analytical models of transient thermoelastic deformations of mirrors heated by high power cw laser beams , 1990 .

[12]  Patrice Hello,et al.  Analytical models of thermal aberrations in massive mirrors heated by high power laser beams , 1990 .

[13]  C. Greninger.  Thermally induced wave-front distortions in laser windows. , 1986, Applied optics.

[14]  D. Z. Anderson,et al.  Alignment of resonant optical cavities. , 1984, Applied optics.

[15]  J. Foster,et al.  Thermal Effects in a Nd:YAG Laser , 1970 .

[16]  F. Low.  Low-Temperature Germanium Bolometer , 1961 .