Abstract

Surface light scattering has matured to the extent that it is now possible to envisage the possibility of applying the technique in more demanding environments like microgravity or industrial process monitoring. Such situations will require more compact and robust system designs than the ones that till now have been used in laboratory studies. The generic elements of a system are identified and their impact on system performance is given based on the model presented in.¹ We note that proper use of a grating provides a calibration that is independent of the wavelength. This facilitates the use of cheap unstabilised semiconductor lasers², but the optics may be rather delicate. An implementation with holographic optical elements gives a mechanically very simple and robust system (Fig. 1)³. A concept based on fully integrated optics is obtained by combining a 2D waveguide with diffractive structures for coupling light out of and into the optical “chip”. The waveguide would be combined with the lower hologram. Laser and detectors could be imbedded in the waveguide. Such a system implies a number of conflicting requirements of the integrated optics. A potential solution based on silicon and a rare earth laser is presented. The complexity of the system may be further reduced by the application of intracavity diffractive structures (Fig. 2). By doing this, we essentially eliminate the need for the very high diffraction efficiency required with external diffractive structures and the laser itself may also be used as a detector. However, the simple configuration requires a spacing to the surface that is fixed within a fraction of the optical wavelength.

© 1996 Optical Society of America