Apparatus for modulating a light beam
First Claim
1. A light beam modulator comprising means for modulating a source beam to provide an output beam at any one time on one of a plurality of discrete paths according to a modulation scheme.
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Accused Products
Abstract
A modulation spectroscopy system (1) has an acousto-optic modulator (5) providing a pump beam onto a sample. The modulator receives a light beam from a source (4) and diffracts it to provide an output which is the first order beam, the zeroth order or undeflected beam being terminated and the 2nd and higher orders being negligible and terminated also. The modulator is driven alternately by two drive frequencies at a modulation or toggle frequency. The first order output is at one angle for a first drive frequency and at another angle for the other drive frequency. The duty cycle of alternating between the different drive frequencies sets the output beam position duty cycle for incidence at two different spots on the sample. Also, either or both beams may be position and/or intensity varied by control of the modulator drive frequencies and their amplitudes.
19 Citations
27 Claims
- 1. A light beam modulator comprising means for modulating a source beam to provide an output beam at any one time on one of a plurality of discrete paths according to a modulation scheme.
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20. A light beam modulator as claimed in 1, wherein the modulator comprises a programmably electro-mechanically, electro-optically, or piezoelectrically variable diffractive optic element for switching the output beam between the paths;
- and wherein the modulator comprises means for switchably rotating the plane of polarisation of a linearly polarised pump beam, and routing means for causing the beam to traverse a different spatial path for each polarisation; and
wherein the rotating means comprises a Pockels Cell controlled by a drive voltage.
- and wherein the modulator comprises means for switchably rotating the plane of polarisation of a linearly polarised pump beam, and routing means for causing the beam to traverse a different spatial path for each polarisation; and
Specification