Tunable electro-optic Q-switch, and lasers using same

Claim 2

An electro-optic Q-switch for a laser having a resonant cavity including an output coupler, a gain medium and a retro-reflecting mirror, for mounting in the resonant cavity between the gain medium and the retro-reflecting mirror, the resonant cavity supporting a cavity mode on a lasing axis, comprising: polarizing means, mounted on the lasing axis, for polarizing the cavity mode in a direction of polarization; phase retarding means, comprising an electro-optic substrate having a crystallographic axis, for inducing controllable phase retardation in the cavity mode in response to an applied electric field in the substrate; means for supporting the substrate in the phase retarding means so that the lasing axis lies essentially in a plane of the crystallographic axis 45° from the direction of polarization, and lies at an angle relative to the crystallographic axis; and control means, connected to the phase retarding means, for supplying the applied electric field within the substrate having a first magnitude in a first state and a second magnitude in a second state, wherein in the first state the phase retarding means induces essentially 90° polarization rotation in a round trip for the cavity mode, and in the second state the phase retarding means induces essentially no polarization rotation in a round trip for the cavity mode.

Claim 3

The Q-switch of claim 1, wherein the phase retarding means comprises: a plate of birefringent material, having a fast axis and a slow axis orthogonal to the fast axis, and mounted so that the direction of polarization is essentially 45 degrees from the fast and slow axes, and having an optical thickness along the lasing axis equal to a multiple of λ/4 ±an error, wherein λ equals wavelength of the cavity mode; and wherein the substrate has an angular position relative to the lasing axis, and the means for supporting the substrate in the phase retarding means includes means for adjusting position of the substrate to compensate for the error.

Claim 4

The Q-switch of claim 1, wherein the phase retarding means comprises a Pockels cell.

Claim 5

The Q-switch of claim 1, wherein the phase retarding means comprises: a Pockels cell including the substrate; a plate of birefringent material, having a fast axis and a slow axis orthogonal to the fast axis and mounted so that the direction of polarization is essentially 45 degrees from the fast and slow axes, and having an optical thickness along the lasing axis equal to a multiple of λ/4 ±an error, wherein λ equals wavelength of the cavity mode; and wherein the substrate has an angular position relative to the lasing axis, and the means for supporting the substrate in the phase retarding means includes means for adjusting the angular position of the substrate to compensate for the error.

Claim 6

The Q-switch of claim 1, wherein the magnitude of the applied electric field in the first state is essentially zero volts.

Claim 7

The Q-switch of claim 1, wherein the phase retarding means comprises a longitudinal field Pockels cell.

Claim 12

A laser, comprising: a resonant cavity including an output coupler and a retro-reflecting mirror, for supporting oscillation along a lasing axis of a cavity mode; a gain medium, including means for supplying pump energy to the gain medium to induce laser gain; polarizing means, mounted on the lasing axis in the resonant cavity between the gain medium and the retro-reflecting mirror, for polarizing the cavity mode in a direction of polarization; phase retarding means, mounted in the resonant cavity between the polarizing means and the retro-reflecting mirror, comprising a substrate having a crystallographic axis, for inducing controllable phase retardation in the cavity mode in response to an applied electric field in the substrate; means for supporting the substrate in the phase retarding means so that the lasing axis lies essentially in a plane of the crystallographic axis 45° from the direction of polarization, and lies at an angle relative to the crystallographic axis; and control means, connected to the phase retarding means, for supplying the applied electric field within the substrate having a first magnitude in a first state and a second magnitude in a second state, wherein in the first state the phase retarding means induces an essentially 90° polarization rotation in a round trip for the cavity mode, and in the second state the phase retarding means induces effectively no polarization rotation in a round trip for the cavity mode.

Claim 13

A laser, comprising: a resonant cavity including an output coupler and a retro-reflecting mirror, for supporting oscillation along a lasing axis of a cavity mode; a gain medium, including means for supplying pump energy to the gain medium to induce laser gain; polarizing means, mounted on the lasing axis in the resonant cavity between the gain medium and the retro-reflecting mirror, for polarizing the cavity mode in a direction of polarization; phase retarding means, mounted in the resonant cavity between the polarizing means and the retro-reflecting mirror, comprising a substrate having a crystallographic axis, for inducing controllable phase retardation in the cavity mode in response to an applied electric field in the substrate; means for supporting the substrate in the phase retarding means so that the lasing axis lies essentially in a plane of the crystallographic axis 45° from the direction of polarization, and lies at an angle relative to the crystallographic axis; and control means, connected to the phase retarding means, for supplying the applied electric field within the substrate having a first magnitude in a first state and a second magnitude in a second state, wherein in the first state the phase retarding means induces an essentially 90° polarization rotation in a round trip for the cavity mode, and in the second state the phase retarding means induces effectively no polarization rotation in a round trip for the cavity mode.

Claim 14

The laser of claim 9, wherein the phase retarding means comprises: a plate of birefringent material, having a fast axis and a slow axis orthogonal to the fast axis, and mounted so that the direction of polarization is essentially 45 degrees from the fast and slow axes, and having an optical thickness along the lasing axis equal to a multiple of λ/4 an error, wherein λ equals wavelength of the cavity mode; and wherein the substrate has an angular position relative to the lasing axis, and the means for supporting the substrate in the phase retarding means includes means for adjusting position of the substrate to compensate for the error.

Claim 15

The laser of claim 9, wherein the phase retarding means comprises a Pockels cell.

Claim 16

The laser of claim 9, wherein the phase retarding means comprises: a Pockels cell including the substrate; a plate of birefringent material, having a fast axis and a slow axis orthogonal to the fast axis, and mounted so that the direction of polarization is essentially 45 degrees from the fast and slow axes, and having an optical thickness along the lasing axis equal to a multiple of λ/4 ±an error, wherein λ equals wavelength of the cavity mode; and wherein the substrate has an angular position relative to the lasing axis, and the means for supporting the substrate in the phase retarding means includes means for adjusting position of the substrate to compensate for the error.

Claim 17

The laser of claim 9, wherein the magnitude of the applied electric field in the first state is essentially zero volts.

Claim 18

The laser of claim 9, wherein the phase retarding means comprises a longitudinal field Pockels cell.

Claim 19

The laser of claim 9, further including: means, mounted within the resonant cavity, for tuning the cavity mode over a range of wavelengths; and means, mounted with the means for supporting, for adjusting the angle in cooperation with the means for tuning so that the amount of phase retardation in the first state remains essentially a quarterwave over the range of wavelengths.

Claim 20

A tunable laser, comprising: a resonant cavity including an output coupler and a retro-reflecting mirror, for supporting oscillation of a cavity mode along a lasing axis; a gain medium, including means for supplying pump energy to the gain medium to induce laser gain; means, mounted within the resonant cavity, for tuning the cavity mode over a range of wavelengths; polarizing means, mounted on the lasing axis in the resonant cavity between the gain medium and the retro-reflecting mirror, for polarizing the cavity mode in a direction of polarization; phase retarding means, mounted in the resonant cavity between the polarizing means and the retro-reflecting mirror, comprising a substrate having a crystallographic axis, for inducing controllable phase retardation in the cavity mode in response to an applied electric field in the substrate; means for supporting the substrate in the phase retarding means so that the lasing axis lies essentially in a plane of the crystallographic axis 45° from the direction of polarization, and lies at an angle relative to the crystallographic axis; control means, connected to the phase retarding means, for supplying the applied electric field within the substrate having a first magnitude in a first state and a second magnitude in a second state, wherein in the first state the phase retarding means induces 90° polarization rotation in a round trip for the cavity mode, and in the second state the phase retarding means induces effectively no polarization rotation in a round trip for the cavity mode; and means, mounted with the means for support, for adjusting the angle in cooperation with the means for tuning so that the amount of rotation in the first state remains essentially 90° as the cavity mode is tuned over the range of wavelengths.

Claim 21

A tunable laser, comprising: a resonant cavity including an output coupler and a retro-reflecting mirror, for supporting oscillation of a cavity mode along a lasing axis; a gain medium, including means for supplying pump energy to the gain medium to induce laser gain; means, mounted within the resonant cavity, for tuning the cavity mode over a range of wavelengths; polarizing means, mounted on the lasing axis in the resonant cavity between the gain medium and the retro-reflecting mirror, for polarizing the cavity mode in a direction of polarization; phase retarding means, mounted in the resonant cavity between the polarizing means and the retro-reflecting mirror, comprising a substrate having a crystallographic axis, for inducing controllable phase retardation in the cavity mode in response to an applied electric field in the substrate; means for supporting the substrate in the phase retarding means so that the lasing axis lies essentially in a plane of the crystallographic axis 45° from the direction of polarization, and lies at an angle relative to the crystallographic axis; control means, connected to the phase retarding means, for supplying the applied electric field within the substrate having a first magnitude in a first state and a second magnitude in a second state, wherein in the first state the phase retarding means induces 90° polarization rotation in a round trip for the cavity mode, and in the second state the phase retarding means induces effectively no polarization rotation in a round trip for the cavity mode; and means, mounted with the means for support, for adjusting the angle in cooperation with the means for tuning so that the amount of rotation in the first state remains essentially 90° as the cavity mode is tuned over the range of wavelengths.

Claim 22

The laser of claim 16, wherein the phase retarding means comprises a Pockels cell.

Claim 23

The laser of claim 16, wherein the magnitude of the applied electric field in the first state is essentially zero volts.

Claim 24

The laser of claim 16, wherein the phase retarding means comprises a longitudinal field Pockels cell.

Claim 25

The laser of claim 16, wherein the phase retarding means comprises: a Pockels cell including the substrate; a plate of birefringent material, having a fast axis and a slow axis orthogonal to the fast axis and mounted so that the direction of polarization is essentially 45 degrees from the fast and slow axes, and having an optical thickness along the lasing axis equal to a multiple of λ/4 ±an error, wherein λ equals a wavelength within the range of wavelengths of the cavity mode, and the error changes as the wavelength of the cavity mode is changed; and wherein the substrate has an angular position relative to the lasing axis, and the means for supporting the substrate in the phase retarding means includes means for adjusting the angular position of the substrate to compensate for the error.

Claim 26

The laser of claim 16, wherein the phase retarding means comprises: a Pockels cell including the substrate; an achromatic quarterwave plate, having a fast axis and a slow axis orthogonal to the fast axis and mounted so that the direction of polarization is essentially 45 degrees from the fast and slow axes, inducing phase retardation of λ/4 ±an error, wherein λ equals a wavelength within a range of wavelengths; and wherein the substrate has an angular position relative to the lasing axis, and the means for supporting the substrate in the phase retarding means includes means for adjusting the angular position of the substrate to compensate for the error.

Claim 27

A tunable laser, comprising: a resonant cavity, including an output coupler, for supporting oscillation of a cavity mode along a lasing axis; a gain medium, including means for supplying pump energy to the gain medium to induce laser gain; means, mounted within the resonant cavity, for tuning the cavity mode over a range of wavelengths; and an electro-optic Q-switch, mounted within the resonant cavity, including means for tuning the Q-switch over the range of wavelengths.

Claim 28

A tunable laser, comprising: a resonant cavity, including an output coupler, for supporting oscillation of a cavity mode along a lasing axis; a gain medium, including means for supplying pump energy to the gain medium to induce laser gain; means, mounted within the resonant cavity, for tuning the cavity mode over a range of wavelengths; and an electro-optic Q-switch, mounted within the resonant cavity, including means for tuning the Q-switch over the range of wavelengths.

Claim 29

The tunable laser of claim 22, wherein the electro-optic Q-switch comprises a Pockels cell.

Claim 30

The tunable laser of claim 22, wherein the gain medium comprises Ti:Sapphire.