Pulse compression

• US 4,750,809 A
• Filed: 05/01/1985
• Issued: 06/14/1988
• Est. Priority Date: 05/01/1985
• Status: Expired due to Term

• Current Assignee: Spectra-Physics Lasers, Inc. (Perspecta, Inc.)
• Original Assignee: Spectra-Physics Incorporated (MKS Instruments Incorporated)
• Inventors: Kolner, Brian H., Bloom, David M., Baer, Thomas M., Kafka, James D.
• Primary Examiner(s): ARNOLD, BRUCE
• Application Number:
  US06/729,376
• Time in Patent Office: 1,140 Days
• Field of Search: 350/162.11, 350/320, 350/168, 350/162.17
• US Class Current: 359/566
• CPC Class Codes: H01S 3/0057 Temporal shaping, e.g. pulse compression, frequency chirping soliton generation and propagation G02F1/3513, H01S3/063 and H01S3/108
• CPC Class Codes: Y10S 359/90 Methods

Abstract

A pulse compressor compresses a relatively long width optical pulse (of the kind which may be transform limited) to a short width pulse. The compressor includes a color generator which broadens the bandwidth of the long pulse to include any additional colors required for compression to the short pulse. The compressor also includes a grating which has a groove spacing and which is aligned with the output of the color generator at a grazing incidence angle effective for producing a compact grating structure, reduced ellipticity of the beam output from the compressor and high efficiency of light transmission through the device.

Claims

1. Pulse compressor apparatus for compressing a relatively long width optical pulse of the kind which may be transform limited to a shorter width pulse, said apparatus comprising,

color generator means for generating from the long pulse an output beam having a bandwidth broadened to include any additional colors required for compression of the long pulse to the shorter pulse, and

dispersive delay line means for compressing the output of the color generator means to the short width pulse.

said dispersive delay line means including grating means aligned with the beam from the output of the color generator means at a grazing incidence angle of about 60 degrees to 89 degrees between the beam and the normal to the grating means, effective for producing a compact grating means structure, and at the same time with a groove spacing selected to operate in near-Littrow condition, i.e. wherein the angle between the beam incident on the grating means and the beam diffracted from the grating means is small, the groove spacing and near-Littrow condition providing greater than 80% efficiency of light transmission through the grating means.

2. The invention defined in claim 1 wherein the color generator means include an optical fiber.

3. The invention defined in claim 1 wherein the wavelength of the optical pulse to be compressed is 1064 nanometers and the grating means have 1700 to 1800 lines per millimeter.

4. The invention defined in claim 1 wherein the width of the pulse to be compressed is on the order of 100 picoseconds and the spacing between the grating and a beam redirection means which returns the beam toward the grating is less than 40 centimeters.

5. The invention defined in claim 1 wherein the dispersive delay line means include a single grating and a roof prism reflector.

6. The invention defined in claim 1 wherein the dispersive delay line means includes a single grating and two roof prism reflectors, so that the beam is refracted four times off the grating and produces essentially a spatially round beam.

7. The invention defined in claim 1 wherein the grating means are aligned with the beam from the output of the color generator at a grazing incidence angle which permits working far enough back on the flat part of the dispersion curve to accommodate the spread of angles inherent in the beam containing the optical pulse.

8. A method compressing a relatively long width optical pulse of the kind which may be transform limited to a shorter width pulse, said method comprising,

generating in a color generator an output beam having a bandwidth broadened to include any additional colors required for compression of the long pulse to the shorter pulse, and

compressing in a dispersive delay line structure the output of the color generator,

the compressing step including directing the beam from the color generator onto grating means, and selecting a groove spacing such that, for a given wavelength beam, the exit angle of the beam from the grating is steep, in the range of about 60 degrees to 89 degrees, and the grating operates in near-Littrow condition, i.e. wherein the angle between the beam incident on the grating means and the beam diffracted from the grating means is small, whereby compactness of the dispersive delay line is achieved through steepness of the exit angle, and wherein the groove spacing is selected to provide optimum efficiency, greater than about 80%.

9. The method of claim 8, wherein the given wavelength is 1064 nanometers and the grating means has a groove spacing of about 1600 to 1800 lines per millimeter.

10. A compact pulse compression apparatus for compressing a 1064 nanometer optical pulse of relatively long widths produced by a CW mode-locked Nd-YAG laser at high efficiency of beam transmission, comprising,

color generator means for generating from the long pulse an output beam having a bandwidth broadened to include any additional colors required for compression of the long pulse to the shorter pulse, and

dispersive delay line means for compressing the output of the color generator means to the short width pulse,

the dispersive delay line means including grating means having a groove spacing of 1600 to 1800 lines per millimeter and being aligned with respect to the beam from the output of the color generator means at a grazing incidence angle of about 60 degrees to 89 degrees between the beam and the normal to the grating means, for producing a compact dispersive delay line means, and with the groove spacing to allow grazing incidence and to produce grating means operation in near-Littrow condition, i.e. wherein the angle between the beam incident on the grating means and the beam diffracted from the grating means is small, the groove spacing and near-Littrow condition providing high efficiency of light transmission through the grating means.

11. The pulse compression apparatus of claim 10, wherein the grating means has a groove spacing of about 1700 lines per millimeter and the incidence angle is about 70 degrees.