Photodetector arrangement for measuring the state of polarization of light

Claim 3

The apparatus of claim 1 wherein the photodetector is positioned to intercept the light beam at an oblique angle of incidence.

Claim 4

The apparatus of claim 1 further including means for determining at least one parameter of the state of polarization of the light beam from said electrical output signal.

Claim 5

The apparatus of claim 1 further including means for rotating said at least one photodetector around an axis defined by the incident light beam.

Claim 6

The apparatus of claim 1 wherein there are two of said polarization sensitive photodetectors such that; (a) a first of said photodetectors partially reflects the light beam incident thereon and produces a first electrical output signal having a magnitude proportional to the radiation absorbed by the first photodetector; and (b) a second of said photodetector being positioned so that the light beam partially reflected from the first photodetector is incident on said second photodetector and produces a second electrical output signal having a magnitude proportional to the radiation absorbed by the second photodetector.

Claim 7

The apparatus of claim 3 wherein said means for determining the at least one parameter of the state of polarization includes a microcomputer.

Claim 8

An ellipsometer for measuring the state of polarization of a light beam comprising: (a) a photodetector having a partially specularly reflecting surface on which the light beam is incident at an oblique angle with a plane of incidence and is partially reflected therefrom, said photodetector producing an electrical output signal having a magnitude proportional to the radiation absorbed by the photodetector; and (b) means coupled to said photodetector for rotating said photodetector around an axis defined by the incident light beam to modulate the electrical output signal.

Claim 9

An ellipsometer for measuring the state of polarization of a light beam comprising: (a) a photodetector having a partially specularly reflecting surface on which the light beam is incident at an oblique angle with a plane of incidence and is partially reflected therefrom, said photodetector producing an electrical output signal having a magnitude proportional to the radiation absorbed by the photodetector; and (b) means coupled to said photodetector for rotating said photodetector around an axis defined by the incident light beam to modulate the electrical output signal.

Claim 10

The ellipsometer of claim 7 wherein said rotating means includes a synchronous or stepping motor.

Claim 11

The ellipsometer of claim 7 further including means coupled to said modulated electrical output signal for determining the state of polarization of a light beam.

Claim 12

The ellipsometer of claim 7 wherein said rotating means rotates the photodetector such that said photodetector precesses about an axis normal to said specularly reflecting surface whereby said light partially reflected therefrom is a conically rotating reflecting light beam.

Claim 13

The ellipsometer of claim 7 further including means for determining the azimuth angle of the plane of incidence of the light beam.

Claim 14

The ellipsometer of claim 11 wherein said means for determining the azimuth angle includes an auxiliary photodetector that intercepts the light beam reflected from said specularly reflecting photodetector, said auxiliary photodetector producing an auxiliary electrical output signal in the form of a timing pulse.

Claim 15

The ellipsometer of claim 12 further including a plurality of said auxiliary photodetectors positioned around said specularly reflecting photodetector to intercept the rotating reflected light beam at a plurality of angles to provide an angular encoding scheme for converting said modulated electrical output signals to corresponding digital signals.

Claim 16

The ellipsometer of claim 13 further including means coupled to receive said corresponding digital signals for calculating the elliptic polarization of a light beam.

Claim 17

The ellipsometer of claim 13 wherein said calculating mean is a microcomputer having calibration data obtained with a linearly polarized light beam stored therein.

Claim 18

The ellipsometer of claim 12 including means coupled to said modulated electrical output signal and said auxiliary output signal for determining the input state of polarization of a light beam with respect to a reference plane of incidence of the light beam.

Claim 19

The ellipsometer of claim 16 wherein said means for determining the input state of polarization includes a microcomputer having calibration data stored therein.

Claim 22

The apparatus of claim 18 wherein the light beam incident on the first photodetector and the partially reflected light beam incident on the second photodetector are incident at a common plane of incidence.

Claim 23

The apparatus of claim 19 wherein the detecting surface of said second detector is a partially specularly reflecting surface.

Claim 24

The apparatus of claim 20 wherein the partially reflected light beam is incident on said second photodetector at an oblique angle.

Claim 25

The apparatus of claim 19 wherein the detecting surface of said second detector is a substantially totally light absorptive surface.

Claim 26

The apparatus of claim 22 wherein the partially reflected light beam is incident on said second photodetector normal to the detecting surface of said second photodetector.

Claim 27

The apparatus of claim 20 or 22 wherein the detecting surface of said first and second photodetectors are parallel to each other.

Claim 29

The apparatus of claim 24 including means for rotating the first and second photodetector as an integral unit by a predetermined angle with respect to the light beam incident on the first photodetector, said first photodetector producing a third electrical output signal at the rotated position and the second photodetector producing a fourth electrical output signal at the rotated position.

Claim 30

The apparatus of claim 26 including means coupled to receive said first, second, third and fourth electrical output signals for determining the state of polarization of the light beam.

Claim 31

An ellipsometer for measuring the state of polarization of a light beam, comprising: (a) a first photodetector having a partially specularly reflecting detecting surface in which the light beam is incident at an oblique angle with a first plane of incidence and is partially reflected therefrom, said first photodetector producing a first electrical output signal having a magnitude proportional to the radiation absorbed by the first photodetector; (b) a second photodetector having a detecting surface on which the light beam partially reflected from the first photodetector is incident at a plane of incidence, substantially coincident with the first plane of incidence, said second photodetector producing a second electrical output signal having a magnitude proportional to the radiation absorbed by the second photodetector; (c) means for rotating the plane of incidence of the light beam incident on the first photodetector to a second plane of incidence different from the first plane of incidence, said first photodetector producing a third electrical output signal at the second plane of incidence and the second photodetector producing a fourth electrical output signal at the second plane of incidence.

Claim 32

An ellipsometer for measuring the state of polarization of a light beam, comprising: (a) a first photodetector having a partially specularly reflecting detecting surface in which the light beam is incident at an oblique angle with a first plane of incidence and is partially reflected therefrom, said first photodetector producing a first electrical output signal having a magnitude proportional to the radiation absorbed by the first photodetector; (b) a second photodetector having a detecting surface on which the light beam partially reflected from the first photodetector is incident at a plane of incidence, substantially coincident with the first plane of incidence, said second photodetector producing a second electrical output signal having a magnitude proportional to the radiation absorbed by the second photodetector; (c) means for rotating the plane of incidence of the light beam incident on the first photodetector to a second plane of incidence different from the first plane of incidence, said first photodetector producing a third electrical output signal at the second plane of incidence and the second photodetector producing a fourth electrical output signal at the second plane of incidence.

Claim 33

The ellipsometer of claim 28 wherein the detecting surface of said first and second photodetectors are parallel to each other.

Claim 34

The ellipsometer of claim 29 including means coupled to said first, second, third and fourth electrical output signals for measuring the polarization parameters ψ and cos Δ.

Claim 35

The ellipsometer of claim 30 including means for storing calibration data to thereby determine the state of polarization of the light beam.

Claim 36

The apparatus of claim 28 wherein the detecting surface of said second detector is a partially specularly reflecting surface.

Claim 37

The apparatus of claim 28 wherein the partially reflected light beam is incident on said second photodetector at an oblique angle.

Claim 38

The apparatus of claim 28 wherein the detecting surface of said second detector is a substantially totally light absorptive surface.

Claim 39

The ellipsometer of claim 28 wherein said is provided by a half-wave retarder inserted within the light beam incident on the first photodetector.

Claim 40

The ellipsometer of claim 35 wherein said half-wave retarder is an electro-optical retarder.

Claim 41

The ellipsometer of claim 35 wherein said half-wave retarder is a piezo-optical retarder.

Claim 42

The ellipsometer of claim 28 wherein said rotating means includes a stepping motor.

Claim 45

The method of claim 39 further including the step of rotating the photodetector around an axis defined by the incident light beam.