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A Simple Solar-Blind Photodiode for Light Near 200 nm Useful For Angle-Locking Nonlinear Optical Crystals

IP.com Disclosure Number: IPCOM000102846D
Original Publication Date: 1990-Feb-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 1 page(s) / 40K

Publishing Venue

IBM

Related People

Bethune, DS: AUTHOR [+2]

Abstract

A simple solar-blind split-cathode photodiode has been devised for use in controlling the orientation of a nonlinear optical crystal such as beta-Barium Borate (BBO) to maintain optimum conversion of pump light to tunable ultraviolet radiation in the 200 nm region. This device avoids the need for any wavelength filtering and is rugged, inexpensive and easy to build. It functions by using a pair of cathodes which are inherently insensitive to long wavelengths to monitor the position of the short-wavelength beam of light. The cathode work function is sufficiently large that the long wavelength pump-beam photons will not cause electrons to be emitted from the surface. Many common metals, such as stainless steel and copper have work functions of about 4.5 V, giving long-wavelength cutoffs of about 275 nm.

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A Simple Solar-Blind Photodiode for Light Near 200 nm Useful For Angle-Locking Nonlinear Optical Crystals

      A simple solar-blind split-cathode photodiode has been devised
for use in controlling the orientation of a nonlinear optical crystal
such as beta-Barium Borate (BBO) to maintain optimum conversion of
pump light to tunable ultraviolet radiation in the 200 nm region.
This device avoids the need for any wavelength filtering and is
rugged, inexpensive and easy to build.  It functions by using a pair
of cathodes which are inherently insensitive to long wavelengths to
monitor the position of the short-wavelength beam of light.  The
cathode work function is sufficiently large that the long wavelength
pump-beam photons will not cause electrons to be emitted from the
surface.  Many common metals, such as stainless steel and copper have
work functions of about 4.5 V, giving long-wavelength cutoffs of
about 275 nm.  An anode grid placed as close to the cathode surfaces
as practical and biased to a positive voltage collects the
photocurrent.  The device operates in ambient air without a window
and is naturally very rugged, being composed of, for example,
stainless steel and tungsten, and can withstand very intense
laser-based radiation without damage.  The device described here is
thus very well suited for use in a crystal orientation control system
for optimized harmonic generation or sum-frequency mixing, and can
also serve as a pulse energy monitor.

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