# US 5,703,713 A · Multi-wavelength variable attenuator and half wave plate

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- Number: US 5,703,713 A
- Document ID: US5703713A
- Status: Granted
- Kind: A
- Application number: 08/455,509
- Filed: 1995-05-31
- Granted: 1997-12-30
- Earliest claimed: 1994-02-18
- Assignees: New Wave Research
- Inventors: Tony P. Leong; Edward S. North; Richard Linsley Herbst
- Web page: https://patentgrep.com/patent/US5703713A

## CPC

- B23K 26/0665: {by beam condensation on the workpiece, e.g. for focusing}
- B23K 26/032: {using optical means}
- B23K 26/06: Shaping the laser beam, e.g. by masks or multi-focusing
- B23K 26/0648: {comprising lenses}
- G02B 5/3083: {Birefringent or phase retarding elements (G02B5/3008, G02B5/3016 take precedence; systems for polarisation control G02B27/286; manufacturing phase modulating patterns by lithographic processes G03F7/001)}
- G02B 26/007: {the movable or deformable optical element controlling the colour, i.e. a spectral characteristic, of the light}
- G02B 26/023: {comprising movable attenuating elements, e.g. neutral density filters}
- G02F 1/37: for second-harmonic generation {(G02F1/3532 takes precedence)}
- H10P 74/232: {comprising connection or disconnection of parts of a device in response to a measurement}
- G02F 1/1309: {Repairing; Testing}
- G02F 1/354: {Third or higher harmonic generation}
- B23K: SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10

## Abstract

A probe station which comprises a base machine, a chuck mounted on the base machine to hold a device under test (DUT), a probe platen mounted on the base machine on which to mount probes for the device, a microscope mounted on the base machine having a field of view on the DUT on the chuck, and a single laser, mounted with the microscope. The single laser supplies an output beam in a plurality of wavelengths through the microscope optics on a beam line to the field of view of the microscope. The laser system includes a solid state laser, a harmonic generator coupled with the solid state laser, and switchable optics for selecting the wavelength of the output beam from among two or more selectable wavelengths. In addition, the laser system includes a variable attenuator, based on a unique half-wave plate, which operates for the plurality of wavelengths which are selectable as outputs in the infrared (1064 nanometers), in the green (532 nanometers), and in the ultraviolet (355 nanometers, or 266 nanometers). These wavelengths correspond to the fundamental output wavelength of the Nd:YAG laser, the second harmonic, and either the third or fourth harmonic of the laser.

## Claims

### Claim 1

A multiple wavelength variable attenuator comprising:
a multiple wavelength wave plate which functions as a half-wave plate for at least three wavelengths selected from the group consisting of a fundamental wavelength of a laser, a second harmonic of the fundamental wavelength, a third harmonic of the fundamental wavelength and a fourth harmonic of the fundamental wavelength;
a polarizer; and
a mechanism to control relative angular position of the multiple wavelength wave plate and the polarizer to provide controllable attenuation of at least three wavelengths selected from the group consisting of the fundamental wavelength, the second harmonic of the fundamental wavelength, the third harmonic of the fundamental wavelength and the fourth harmonic of the fundamental wavelength.

### Claim 2 (depends on 1)

The attenuator of claim 1, wherein the multiple wavelength wave plate has an optical thickness of about a 63rd half-wave of the fourth harmonic.

### Claim 3 (depends on 1)

The attenuator of claim 1, wherein the polarizer comprises a calcite polarizer.

### Claim 4 (depends on 1)

The attenuator of claim 1, wherein the multiple wavelength wave plate consists of a single plate of crystalline quartz having a thickness equal to or less than about 1 millimeter.

### Claim 5 (depends on 1)

The attenuator of claim 1, wherein the multiple wavelength wave plate functions as a half-wave plate for the fundamental wavelength, the second harmonic of the fundamental wavelength, and the third harmonic of the fundamental wavelength.

### Claim 6 (depends on 1)

The attenuator of claim 1, wherein the multiple wavelength wave plate functions as a halfwave plate for the fundamental wavelength, the second harmonic of the fundamental wavelength, and the fourth harmonic of the fundamental wavelength.

### Claim 7 (depends on 1)

The attenuator of claim 1, wherein the multiple wavelength wave plate functions as a half-wave plate for the fundamental wavelength, the second harmonic of the fundamental wavelength, the third harmonic of the fundamental wavelength and the fourth harmonic of the fundamental wavelength.

### Claim 8

A multiple wavelength variable attenuator comprising:
a multiple wavelength wave plate which functions as a half-wave plate for at least three wavelengths selected from the group consisting of a fundamental wavelength of about 1064 nanometers, a second harmonic of the fundamental wavelength, a third harmonic of the fundamental wavelength and a fourth harmonic of the fundamental wavelength;
a polarizer; and
a mechanism to control relative angular position of the multiple wavelength wave plate and the polarizer to provide controllable attenuation of at least three wavelengths selected from the group consisting of the fundamental wavelength, the second harmonic of the fundamental wavelength, the third harmonic of the fundamental wavelength and the fourth harmonic of the fundamental wavelength.

### Claim 9 (depends on 8)

The attenuator of claim 8, wherein the multiple wavelength wave plate has an optical thickness of about a 63rd half-wave of the fourth harmonic.

### Claim 10 (depends on 8)

The attenuator of claim 8, wherein the multiple wavelength wave plate consists of a single plate of crystalline/quartz having a thickness equal to or less than about 1 millimeter.

### Claim 11 (depends on 8)

The attenuator of claim 8, wherein the multiple wavelength wave plate functions as a half-wave plate for the fundamental wavelength, the second harmonic of the fundamental wavelength, and the third harmonic of the fundamental wavelength.

### Claim 12 (depends on 8)

The attenuator of claim 8, wherein the multiple wavelength wave plate functions as a half-wave plate for the fundamental wavelength, the second harmonic of the fundamental wavelength, and the fourth harmonic of the fundamental wavelength.

### Claim 13 (depends on 8)

The attenuator of claim 8, wherein the multiple wavelength wave plate functions as a half-wave plate for the fundamental wavelength, the second harmonic of the fundamental wavelength, the third harmonic of the fundamental wavelength and the fourth harmonic of the fundamental wavelength.

### Claim 14 (depends on 8)

The attenuator of claim 8, wherein the multiple wavelength wave plate consists of a single plate of crystalline quartz having a thickness of about 0.779 millimeters.

### Claim 15

A multiple wavelength variable attenuator comprising:
a single plate of crystalline quartz having a thickness selected from the group consisting of about 0.0865 millimeters, 0.3091 millimeters, and 0.5564 millimeters, 0.779 millimeters, and 0.9274 millimeters which functions as a half-wave plate for at least three wavelengths selected from the group consisting of a fundamental wavelength of about 1064 nanometers, a second harmonic of the fundamental wavelength, a third harmonic of the fundamental wavelength and a fourth harmonic of the fundamental wavelength;
a polarizer; and
a mechanism to control relative angular position of the multiple wavelength wave plate and the polarizer to provide controllable attenuation of at least three wavelengths selected from the group consisting of the fundamental wavelength, the second harmonic of the fundamental wavelength, the third harmonic of the fundamental wavelength and the fourth harmonic of the fundamental wavelength.