Laser light source apparatus, and method for controlling temperature of wavelength conversion element in laser light source apparatus

Patent metadata

Field	Value
Publication number	US-9385505-B2
Application number	US-201314394150-A
Country	US
Kind code	B2
Filing date	Mar 28, 2013
Priority date	Apr 19, 2012
Publication date	Jul 5, 2016
Grant date	Jul 5, 2016

Abstract

The wavelength of fundamental wave light emitted from a semiconductor laser is converted by a wavelength conversion element, and the wavelength-converted light is emitted. A power supply circuit feeds electric power to the semiconductor laser. A control part controls an amount of electric power to be fed to a heater such that the wavelength conversion element becomes a temperature that optimizes the wavelength conversion efficiency. Temperatures detected by an element temperature detector and a light source part temperature detector are introduced to the control part, and the control part takes a wavelength conversion element temperature, at which a temperature detected by the light source part temperature detector is minimum, as a set temperature that makes the wavelength conversion efficiency optimal, and feedback-controls the wavelength conversion element temperature such that the wavelength conversion element temperature is at the set temperature by controlling the heating quantity of the heater.

First claim

The invention claimed is:

1. A laser light source apparatus comprising:
a light source part having a semiconductor laser, a wavelength conversion element configured to convert a wavelength of a laser beam emitted from the semiconductor laser, and an external resonator configured to select that laser beam which has a prescribed wavelength from the laser beam released from the wavelength conversion element and reflect the selected laser beam toward the semiconductor laser;
a power supply circuit configured to feed electric power to the semiconductor laser;
an element temperature detecting unit configured to detect temperature of the wavelength conversion element;
a heating unit configured to heat the wavelength conversion element;
a control part configured to control the power supply circuit;
a light source part temperature detecting unit configured to detect temperature of the light source part, the temperature of the light source part not including the temperature of the wavelength conversion element;
an optimal temperature setting unit configured to, when the wavelength conversion element is irradiated with the laser beam, configured to measure a plurality of light source part temperatures with the light source part temperature detecting unit, configure to measure a plurality of wavelength conversion element temperature with the element temperature detecting unit in connection with said plurality of light source part temperature, configured to select lowest light source part temperature from said plurality of light source part temperatures, configured to find wavelength conversion element temperature corresponding to the lowest light source part temperature, and configured to take the wavelength conversion element temperature corresponding to the lowest light source part temperature as an optimal temperature of the wavelength conversion element; and
a temperature controller configured to control an amount of electric power to be supplied to the heating unit based on a difference between the temperature of the wavelength conversion element detected by the element temperature detecting unit and the optimal temperature such that the temperature of the wavelength conversion element becomes the optimal temperature.

2. The laser light source apparatus according to claim 1 , further comprising:
an optimal temperature sequentially setting unit configured to calculate a correction value to the optimal temperature of the wavelength conversion element, with the light source part temperature and/or a condition of the electric power to be supplied to the laser being a parameter, and correct the optimal temperature with the correction value.

3. A method of controlling temperature of a wavelength conversion element of a laser light source apparatus,
the laser light source apparatus including:
a light source part having a semiconductor laser, the wavelength conversion element configured to convert a wavelength of a laser beam emitted from the semiconductor laser, and an external resonator configured to select that laser beam which has a prescribed wavelength from the laser beam released from the wavelength conversion element and reflect the selected laser beam toward the semiconductor laser;
a power supply circuit configured to feed electric power to the semiconductor laser;
an element temperature detecting unit configured to detect the temperature of the wavelength conversion element;
a light source part temperature detecting unit configured to detect light source part temperature, the light source part temperature not including the temperature of the wavelength conversion element; and
a heating unit configured to heat the wavelength conversion element, the laser light source apparatus being configured to control an amount of electric power to be supplied to the heating unit based on a difference between the temperature detected by the element temperature detecting unit and optimal temperature of the wavelength conversion element, and configured to perform control such that the temperature of the wavelength conversion element becomes the optimal temperature of the wavelength conversion element, the method comprising:
altering temperature of the wavelength conversion element and measuring the light source part temperature at the respective temperature of the wavelength conversion element when the wavelength conversion element is irradiated with the laser beam to prepare a plurality of light source part temperatures in connection with a plurality of wavelength conversion element temperatures;
selecting lowest light source part temperature from said plurality of light source part temperatures to find wavelength conversion element temperature corresponding to the lowest light source part temperature;
taking the wavelength conversion element temperature corresponding to the lowest light source part temperature as the optimal temperature of the wavelength conversion element; and
controlling the amount of electric power to be supplied to the heating unit such that the temperature of the wavelength conversion element becomes the optimal temperature of the wavelength conversion element.

4. The method according to claim 3 , further comprising:
calculating a correction value to be applied to the optimal temperature of the wavelength conversion element, with the light source part temperature and/or a condition of electric power to be supplied to the laser being a parameter;
correcting the optimal temperature with the correction value; and
controlling the amount of electric power to be supplied to the heating unit such that the temperature of the wavelength conversion element becomes the corrected optimal temperature.

5. The laser light source apparatus according to claim 1 , wherein the wavelength conversion element includes a periodically poled lithium niobate.

6. The laser light source apparatus according to claim 1 , wherein the semiconductor laser emits infrared light, and the wavelength conversion element converts the infrared light to visible light.

7. The laser light source apparatus according to claim 1 , wherein the light source temperature detecting unit includes a thermistor.

8. The laser light source apparatus according to claim 1 , wherein the external resonator includes a volume Bragg grating.

9. The laser light source apparatus according to claim 2 , wherein the wavelength conversion element includes a periodically poled lithium niobate.

10. The laser light source apparatus according to claim 2 , wherein the semiconductor laser emits infrared light, and the wavelength conversion element converts the infrared light to visible light.

11. The laser light source apparatus according to claim 2 , wherein the light source temperature detecting unit includes a thermistor.

12. The laser light source apparatus according to claim 2 , wherein the external resonator includes a volume Bragg grating.

13. The laser light source apparatus according to claim 2 , wherein the optimal temperature sequentially setting unit calculates the correction value at fixed intervals, and corrects the optimal temperature at the fixed intervals.

14. The method according to claim 4 further comprising periodically performing said calculating a correction value to be applied to the optimal temperature, said correcting the optimal temperature with the correction value, and said controlling the amount of electric power to be supplied to the heating unit.

Assignees

• Ushio Electric Inc

Inventors

• Sugihara Nobuhiko
• Yoshida Kazuhiro
• Fujita Kentaro
• Samejima Takanori

Classifications

• H01S5/02296

  Electricity · mapped topic

• H01S5/141

  using a wavelength selective device, e.g. a grating or etalon (H01S5/146 takes precedence) · CPC title

• H01S5/0617

  using memorised or pre-programmed laser characteristics · CPC title

• H01S5/14

  External cavity lasers (H01S5/18 takes precedence; mode locking H01S5/065) · CPC title

• H01S3/109

  Frequency multiplication, e.g. harmonic generation · CPC title