Laser beam generator including automatic resonator length control

• US 5,339,324 A
• Filed: 07/22/1993
• Issued: 08/16/1994
• Est. Priority Date: 07/28/1992
• Status: Expired due to Term

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Eguchi, Naoya, Oka, Michio
• Primary Examiner(s): Healy, Brian
• Application Number:
  US08/096,346
• Time in Patent Office: 390 Days
• Field of Search: 372/21, 372/22, 372/29, 372/32, 372/23, 372/38, 372/92, 372/98, 372/99, 372/107, 372/108, 372/18, 372/19
• US Class Current: 372/29.022
• CPC Class Codes: G02F 1/3542 Multipass arrangements, i.e. arrangements to make light pass multiple times through the same element, e.g. using an enhancement cavity
• CPC Class Codes: G02F 1/37 for second-harmonic generation G02F1/3532 takes precedence
• CPC Class Codes: H01S 3/0092 Nonlinear frequency conversion, e.g. second harmonic generation [SHG] or sum- or difference-frequency generation outside the laser cavity nonlinear frequency conversion per se G02F1/35
• CPC Class Codes: H01S 3/1398 by using a supplementary modulation of the output

Abstract

A laser beam generator for making wavelength conversion automatically controls the length of an external resonator of a laser source to perform wavelength conversion at a high efficiency by pulling-in a servo using a resonator length error signal and a reflected light signal. A sample-and-hold circuit is used to detect the error signal from the detected light signal which is reflected from the external resonator.

Claims

1. A laser beam generator for generating a wavelength converted laser beam comprising:

a source of light;

an external resonator;

a pair of reflecting means provided at said external resonator;

a nonlinear optical crystal provided in said external resonator and provided an incident laser beam from said source of light thereto;

a moving means for moving at least one of said pair of reflecting means in an optical axis direction and making resonator length control; and

wherein said moving means is supplied with a resonator length error signal due to a deviation between the length of said external resonator and that to said incident laser beam and with a reflected signal from said resonator as a result of reflection of said incident laser beam from said resonator as pulling-in signals for resonator length servo.

3. A laser beam generator according to claim 1, a zero-cross level of said resonator length error signal and a certain level or above of said reflected light signal are detected to user as said pulling-in signal for said resonator length servo.

5. A laser beam generator according to claim 1, said resonator length error signal is generated by a synchronous detecting means.

7. A laser beam generator according to claim 1, said moving means of said reflecting means is vibrated at a certain frequency so that said incident laser beam to said external resonator is modulated in phase.

13. A laser beam generator according to claim 5 wherein said synchronous detecting means is sample-and-hold means.

2. A laser beam generator for generating a wavelength converted laser beam comprising:

a source of light;

a resonator;

a pair of reflecting means provided at said resonator;

a nonlinear optical crystal provided in said resonator and provided an incident laser beam from said source of light thereto;

a laser medium provided between said pair of reflecting means;

a moving means for moving at least one of said pair of reflecting means in an optical axis direction and making resonator length control; and

wherein said moving means is supplied with a resonator length error signal due to a deviation between the length of said resonator and that to said incident laser beam and with a reflected signal from said resonator as a result of reflection of said incident laser beam from said resonator as pulling-in signals for resonator length servo.

4. A laser beam generator according to claim 2, a zero-cross level of said resonator length error signal and a certain level or above of said reflected light signal are detected to user as said pulling-in signal for said resonator length servo.

6. A laser beam generator according to claim 2, said resonator length error signal is generated by a synchronous detecting means.

8. A laser beam generator according to claim 2, said moving means of said reflecting means is vibrated at a certain frequency so that said incident laser beam to said external resonator is modulated in phase.

14. A laser beam generator according to claim 6 wherein said synchronous detecting means is sample-and-hold means.

9. A laser beam generator for generating a wavelength converted laser beam comprising:

a source of light;

a external resonator;

a pair of reflecting means provided at said external resonator;

a nonlinear optical crystal provided in said resonator and provided an incident laser beam from said source of light thereto;

a moving means for moving at least one of said pair of reflecting means in an optical axis direction and making resonator length control; and

wherein said moving means is supplied with a resonator length error signal due to a deviation between the length of said external resonator and that to said incident laser beam and with a reflected signal from said resonator as a result of reflection of said incident later beam from said resonator for pulling-in resonator length servo when a zero-cross level of said error signal is detected during a certain time τ

after said resonator length error signal is compared with a certain slice level so that a rising signal is detected.

10. A laser beam generator for generating a wavelength converted laser beam comprising:

a source of light;

a resonator;

a pair of reflecting means provided at said resonator;

a nonlinear optical crystal provided in said resonator and provided an incident laser beam from said source of light thereto;

a laser medium provided between said pair of reflecting means;

a moving means for moving at least one of said pair of reflecting means in an optical axis direction and making resonator length control; and

wherein said moving means is supplied with a resonator length error signal due to a deviation between the length of said resonator and that to said incident laser beam and with a reflected signal from said resonator as a result of reflection of said incident laser beam from said resonator for pulling-in resonator length servo when a zero-cross level of said error signal is detected during a certain time τ

after said resonator length error signal is compared with a certain slice level so that a rising signal is detected.

11. A laser beam generator for generating a wavelength converted laser beam comprising:

a source of light;

a external resonator;

a pair of reflecting means provided at said resonator;

a nonlinear optical crystal provided in said resonator and provided an incident laser beam from said source of light thereto, said incident laser beam of a frequency fc modulated in phase by a frequency fm to produce a phase-modulated signal;

a clock signal generated from said phase-modulated signal and used to sample and hold said phase-modulated signal;

a moving means for moving at least one of said pair of reflecting means in an optical axis direction and making resonator length control; and

wherein said moving means is supplied with a resonator length error signal due to a deviation between the length of said external resonator and that to said incident laser beam and with a reflected signal from said resonator as a result of reflection of said incident laser beam from said resonator as pulling-in signals for resonator length servo.

12. A laser beam generator for generating a wavelength converted laser beam comprising:

a source of light;

a resonator;

a pair of reflecting means provided at said resonator;

a nonlinear optical crystal provided in said resonator and provided an incident laser beam from said source of light thereto;

said incident laser beam of a frequency fc modulated in phaser by a frequency fm to produce a phase-modulated signal;

a clock signal generated from said phase-modulated signal and used to sample and hold said phase-modulated signal;

a laser medium provided between said pair of reflecting means;

a moving means for moving at least one of said pair of reflecting means in an optical axis direction and making resonator length control; and

wherein said moving means is supplied with a resonator length error signal due to a deviation between the length of said resonator and that to said incident laser beam and with a reflected signal from said resonator as a result of reflection of said incident laser beam from said resonator as pulling-in signals for resonator length servo.