Laser apparatus and method to re-tune emission wavelength of wavelength tunable ld

Patent metadata

Field	Value
Publication number	US-2016006212-A1
Application number	US-201514790667-A
Country	US
Kind code	A1
Filing date	Jul 2, 2015
Priority date	Jul 3, 2014
Publication date	Jan 7, 2016
Grant date	—

Abstract

A laser apparatus for tuning the emission wavelength of a wavelength tunable laser diode will be described. The apparatus includes a tunable LD with heaters to tune the emission wavelength of the tunable LD, and a controller to control the power supplied to the heaters. A feature of the laser apparatus is that the controller supplies pre-emphasis power to the heaters before the supplement of the power corresponding to the re-tuned emission wavelength to accelerate the stability of the temperature of the heaters.

First claim

1 . A laser apparatus, comprising
a wavelength tunable laser diode (t-LD) providing a heater; and a controller to control power supplied to the heater to re-tune an emission wavelength of the t-LD by changing the power from first power Pa to second power Pb, wherein the controller supplies pre-emphasis power Pp before supplying the second power Pb, the pre-emphasis power Pp being greater than the second power Pb when the second power Pb is greater than the first power Pa, and supplies the pre-emphasis power Pp smaller than the second power Pb when the second power Pb is smaller than the first power Pa.

2 . The laser apparatus of claim 1 ,
wherein the power Pp is determined by an equation of:
Pp=Pb+K ·( Pb−Pa ),

where K is a coefficient.

3 . The laser apparatus of claim 2 ,
wherein the t-LD provides n (>1) counts of heaters each supplied with first power Pai, second power Pbi, and pre-emphasis power Ppi specific to respective heaters, wherein respective pre-emphasis power Ppi are determined by equations of:
Ppi=Pbi+Ki ×( Pbi−Pai ) i= 1 to n,

wherein Ki is specific to the i-th heater.

4 . The laser apparatus of claim 2 ,
wherein the coefficient K depends on a difference between the first power Pa and the second power Pb.

5 . The laser apparatus of claim 2 ,
wherein the coefficient K depends on a polarity of a difference between the first power Pa and the second power Pb.

6 . The laser apparatus of claim 2 ,
wherein the controller supplies an upper limit instead of the pre-emphasis power Pp when the pre-emphasis power Pp is greater than the upper limit, and supplies a lower limit instead of the pre-emphasis power Pp when the pre-emphasis power Pp is less than the lower limit.

7 . The laser apparatus of claim 1 ,
wherein the controller suspends the supplement of the pre-emphasis power Pp when a difference between the first power Pa and the second power Pb is smaller than a threshold.

8 . The laser apparatus of claim 1 ,
further comprising a wavelength detector to determine a current wavelength emitted from the t-LD, wherein the controller controls the power supplied to the heater by a feedback loop including the wavelength detector from a preset period after setting the second power Pb to the heater.

9 . The laser apparatus of claim 1 ,
further comprising a temperature controller to control a temperature of the t-LD, and an additional heater, wherein the controller controls power supplied to the additional heater such that a sum of the pre-emphasis power Pp and power supplied to the additional heater during the pre-emphasis subtracted by a sum of the first power Pa and power supplied to the additional heater before the pre-emphasis becomes less than the pre-emphasis power Pp subtracted with the first power Pa; and a sum of the second power Pb and power supplied to the additional heater after the pre-emphasis subtracted by the sum of the pre-emphasis power Pp and the power supplied to the additional heater during the pre-emphasis becomes less than the second power Pb subtracted by the pre-emphasis power Pp.

10 . The laser apparatus of claim 1 ,
wherein the t-LD includes n counts of heaters each supplied with first power Pai (i=1 to n) specific to respective heaters before the pre-emphasis, pre-emphasis power Ppi (i=1 to n) specific to respective haters during the pre-emphasis, and second power Pbi (i=1 to n) specific to respective heaters after the pre-emphasis, and an additional heater, wherein the controller controls the power supplied to the additional heater such that a sum of the pre-emphasis power Ppi and the power supplied to the additional heater during the pre-emphasis subtracted with a sum of the first power Pai and the power supplied to the additional heater before the pre-emphasis becomes smaller than a sum of the pre-emphasis power Ppi subtracted with the sum of the first power Pai; and a sum of the second power Pbi and power supplied to the additional heater after the pre-emphasis subtracted with the sum of the pre-emphasis power Ppi and the power supplied to the additional heater during the pre-emphasis becomes smaller than the second power Pbi subtracted with the sum of the pre-emphasis power Ppi.

11 . The laser apparatus of claim 9 ,
wherein the additional heater is mounted on the temperature controller.

12 . The laser apparatus of claim 9 ,
wherein the additional heater is integrated with the t-LD.

13 . The laser apparatus of claim 10 ,
wherein the t-LD includes a chirped sampled grating distributed Bragg reflector (CSG-DBR) region providing at least of heaters and a sampled grating distributed feedback (SG-DFB) region providing at least another one of heaters.

14 . A method to re-tune an emission wavelength of a wavelength tunable LD (t-LD) that integrates a heater to modify a temperature of the t-LD, the t-LD emitting light with a first wavelength stably by being provided with first power Pa, the method comprising steps of:
triggering by a command to re-tune the emission wavelength, providing pre-emphasis power Pp for a preset period to the heater; and supplying second power Pb to the heater, wherein the pre-emphasis power Pp is greater than the second power Pb when the second power Pb is greater than the first Pa but smaller than the second power Pb when the second power Pb is smaller than the first power Pa.

15 . The method of claim 14 ,
wherein the t-LD further provides an additional heater, wherein the step of providing the pre-emphasis power Pp includes a step of providing power to the additional heater such that a sum of the first power Pa and power supplied to the additional heater before triggering becomes equal to a sum of the pre-emphasis power Pp and power supplied to the additional heater during the pre-emphasis, and wherein the step of providing the second power Pb includes a step of providing power to the additional heater such that a sum of the pre-emphasis power Pp and the power supplied to the additional heater during the pre-emphasis becomes equal to a sum of the second power Pb and power supplied to the additional heater after the pre-emphasis.

16 . The method of claim 14 ,
wherein the t-LD further provides an additional heater, wherein the step of providing the pre-emphasis power Pp includes a step of providing power to the additional heater such that a sum of the pre-emphasis power Pp and power supplied to the additional heater during the pre-emphasis subtracted with a sum of the first power Pa and power supplied to the additional heater before the pre-emphasis becomes less than the pre-emphasis power Pp subtracted with the first power Pa, and wherein the step of providing the second power Pb includes a step of providing the second power Pb such that a sum of the second power Pb and power supplied to the additional heater after the pre-emphasis subtracted with a sum of the pre-emphasis power Pp and the power supplied to the additional heater during the pre-emphasis becomes less than the second power Pb subtracted with the pre-emphasis power Pp.

Assignees

• Sumitomo Electric Industries
• Nat Inst Of Advanced Ind Scien

Inventors

• Uesaka Katsumi
• Banno Eiichi
• Shoji Hajime
• Matsuura Hiroyuki
• Kuwatsuka Haruhiko
• Tanizawa Ken
• Namiki Shu

Classifications

• H01S5/02453

  Heating, e.g. the laser is heated for stabilisation against temperature fluctuations of the environment (H01S5/0612 takes precedence, for monolithically integrated heaters see also H01S5/0261) · CPC title

• H01S5/0687 Primary

  Stabilising the frequency of the laser · CPC title

• H01S5/12

  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 title

• H01S5/0265

  Intensity modulators (intra-cavity modulators H01S5/0625) · CPC title

• H01S5/125

  Distributed Bragg reflector [DBR] lasers · CPC title