LIGHT SOURCE APPARATUS AND METHOD OF CONTROLLING THE SAME

• US 20140021865A1
• Filed: 07/15/2013
• Published: 01/23/2014
• Est. Priority Date: 07/18/2012
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Tezuka, Taro
• Granted Patent: US 9,113,507 B2
• Time in Patent Office: Days
• US Class Current: 315/151
• CPC Class Codes: H01S 5/0085 for modulating the output, i.e. the laser beam is modulated outside the laser cavity
• CPC Class Codes: H01S 5/0687 Stabilising the frequency of the laser
• CPC Class Codes: H01S 5/12 the resonator having a periodic structure, e.g. in distributed feedback [DFB] lasers comprising a photonic bandgap structure H01S5/11; surface-emitting lasers H01S5/18
• CPC Class Codes: H01S 5/4087 emitting more than one wavelength
• CPC Class Codes: H05B 47/10 Controlling the light source

Abstract

A light source apparatus configured to emit first light and second light includes a wavelength reference device, a splitter, a first detector, a second detector, and a control unit. The control unit includes a correction unit configured to reduce from a detection signal detected by the first detector a portion included in the detected signal and related to an intensity of the second light incident on the first detector from the splitter, and configured to reduce from a detection signal detected by the second detector a portion included in the detected signal and related to an intensity of the first light incident on the second detector from the splitter. The control unit controls a wavelength of the first light and a wavelength of the second light based on signals from the correction unit.

Claims

1. Alight source apparatus configured to emit first light and second light, the light source apparatus comprising:

a wavelength reference device that the first light and the second light are incident on configured to change intensities of the respective beams of light according to a wavelength deviation of the respective beams of light from a first reference wavelength and a wavelength deviation of the respective beams of light from a second reference wavelength;

a splitter configured to split light containing the first light and light containing the second light from the wavelength reference device from each other;

a first detector configured to detect an intensity of the light containing the first light from the splitter;

a second detector configured to detect an intensity of the light containing the second light from the splitter; and

a control unit configured to control a wavelength of the first light using a detection signal detected by the first detector, such that the wavelength of the first light is the first reference wavelength, and configured to control a wavelength of the second light using a detection signal detected by the second detector, such that the wavelength of the second light is the second reference wavelength,

wherein the control unit includes a correction unit configured to reduce from the detection signal detected by the first detector a portion included in the detected signal and related to the intensity of the second light incident on the first detector from the splitter, and configured to reduce from the detection signal detected by the second detector a portion included in the detected signal and related to the intensity of the first light incident on the second detector from the splitter, and

wherein the control unit controls the wavelength of the first light and the wavelength of the second light based on signals from the correction unit.

2. The light source apparatus according to claim 1, wherein the correction unit comprises:

a first calculator configured to obtain an error signal of the first light from the detection signal detected by the first detector;

a second calculator configured to obtain an error signal of the second light from the detection signal detected by the second detector;

a first attenuator configured to attenuate a part of the error signal of the first light obtained by the first calculator;

a second attenuator configured to attenuate a part of the error signal of the second light obtained by the second calculator;

a first subtractor configured to subtract the error signal of the second light attenuated by the second attenuator from the error signal of the first light obtained by the first calculator; and

a second subtractor configured to subtract the error signal of the first light attenuated by the first attenuator from the error signal of the second light obtained by the second calculator, and

wherein the control unit controls the wavelength of the first light and the second light using the error signal subtracted by the first subtractor and the second subtractor.

3. The light source apparatus according to claim 2, wherein the error signal of the first light is a signal representing a difference between the first reference wavelength and the wavelength of the first light, and

wherein the error signal of the second light is a signal representing a difference between the second reference wavelength and the wavelength of the second light.

4. The light source apparatus according to claim 2, wherein an attenuation factor by which the first attenuator attenuates the part of the error signal of the first light and an attenuation factor by which the second attenuator attenuates the part of the error signal of the second light are obtained from a spectral characteristic of the splitter.

5. The light source apparatus according to claim 4, wherein the spectral characteristic of the splitter is at least one of a transmittance and a reflectance of the splitter at each of the wavelength of the first light and the wavelength of the second light.

6. The light source apparatus according to claim 2, wherein at least one of an attenuation factor by which the first attenuator attenuates the part of the error signal of the first light and an attenuation factor by which the second attenuator attenuates the part of the error signal of the second light is variable.

7. The light source apparatus according to claim 2, wherein an attenuation factor by which the first attenuator attenuates the part of the error signal of the first light and an attenuation factor by which the second attenuator attenuates the part of the error signal of the second light are obtained from a spectral characteristic of the splitter obtained based on detection signals detected by the first detector and the second detector when the first light and the second light have respectively been emitted.

8. The light source apparatus according to claim 1, further comprising a multiplexer configured to combine the first light and the second light different in wavelength from each other,

wherein with respect to the first light and the second light combined by the multiplexer, the wavelength reference device changes, according to the wavelength deviation of the respective beams of light from the first reference wavelength and the wavelength deviation of the respective beams of light from the second reference wavelength, intensity of the respective beams of light.

9. A method of controlling a light source apparatus configured to emit first light and second light, the method comprising:

upon incidence of the first light and the second light, changing intensities of the respective beams of light according to a wavelength deviation of the respective beams of light from a first reference wavelength and a wavelength deviation of the respective beams of light from a second reference wavelength,

splitting the first light and second light from each other into light containing the first light and light containing the second light;

detecting an intensity of the split light containing the first light and an intensity of the split light containing the second light; and

controlling a wavelength of the first light using a detection signal detected in the detecting, such that the wavelength of the first light is the first reference wavelength, and controlling a wavelength of the second light using a detection signal detected in the detecting, such that the wavelength of the second light is the second reference wavelength,

wherein in the controlling, performing correction to reduce a portion which is included in the detection signal of the first light detected in the detecting and which is related to the intensity of the second light, and to reduce a portion which is included in the detection signal of the second light detected in the detecting and which is related to the intensity of the first light, and

controlling the wavelength of the first light and the wavelength of the second light based on signals in the performing correction.