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Ultrafast Optical Delay Line Spectrometer

IP.com Disclosure Number: IPCOM000085308D
Original Publication Date: 1976-Mar-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Jacobowitz, L: AUTHOR

Abstract

An ultrafast optical spectrometer with no moving parts is shown in the drawing. Light from a source 10 is directed by a lens 11 through an optical gate 12, slit 13 and sample 14. Light emerging from the sample is reflected from a mirror 15 onto a grating 16 which disperses the light. A fiber optic delay-line bundle 17 has receiving ends disposed in a linear array to receive light dispersed by grating 16 over a range of wavelengths.

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Ultrafast Optical Delay Line Spectrometer

An ultrafast optical spectrometer with no moving parts is shown in the drawing. Light from a source 10 is directed by a lens 11 through an optical gate 12, slit 13 and sample 14. Light emerging from the sample is reflected from a mirror 15 onto a grating 16 which disperses the light. A fiber optic delay-line bundle 17 has receiving ends disposed in a linear array to receive light dispersed by grating 16 over a range of wavelengths.

The lengths of the various fibers in bundle 17 differ to delay in varying increments the amount of time for each pulse to arrive at a detector 18, such as a photomultiplier tube (PMI). The detector in turn may be connected to an oscilloscope 19 that provides an output trace of intensity versus time or wavelength. The output could also be connected through an analog-to-digital converter to a computer for analyzing the output.

To account for variations of fiber transmission with wavelength, or index of refraction variations if different fiber materials are mixed in the bundle 17, a set of neutral density filters may be inserted into the light path for normalizing each fiber to the rest of the fibers.

It is estimated that the speed of operation will be ultrafast. If the fiber optics are made of a material having an index of refraction of 1.5, it would take a pulse of light approximately 5 nanoseconds to traverse a 1 meter length. If the linear dispersion of grating 16 is assumed to be 3 nanometers...