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Optics Express

Optics Express

  • Editor: Andrew M. Weiner
  • Vol. 21, Iss. 8 — Apr. 22, 2013
  • pp: 10335–10341
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Measurement of gain characteristics of semiconductor lasers by amplified spontaneous emissions from dual facets

M-L Ma, J Wu, Y-Q Ning, F Zhou, M Yang, X Zhang, J Zhang, and G-Y Shang  »View Author Affiliations


Optics Express, Vol. 21, Issue 8, pp. 10335-10341 (2013)
http://dx.doi.org/10.1364/OE.21.010335


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Abstract

In this letter, we describe a novel gain measurement approach for semiconductor edge-emitting lasers, with which TE and TM gain spectra can be easily obtained by collecting the amplified spontaneous emissions at dual facets of the device. An unstrained and continuously-operated GaAs/AlGaAs single quantum well laser strip is used to illustrate this method. The measured gain spectra are compared with theoretical gain curves to analyze the gain polarization characteristics and the relevant subband structure in the valence band of the well using the measured gain spectra.

© 2013 OSA

1. Introduction

Optical gain is an important physical parameter in assessing semiconductor laser performance. Although the gain spectra can be calculated in theory, some problems are always encountered, such as the approximation treatment to some coefficients in equations, because they are difficult to be determined in the calculation. Moreover, the inevitable structure defects of the device resulting from fabrication mean that the gain from completely theoretical calculation represents only an ideal situation of the device performance.

Since the 1970s some methods have been developed to measure the gain of semiconductor lasers and to obtain true gain spectra from actual device operations. The main techniques involve those developed by Hakki-Paoli and Cassidy [1

1. B. W. Hakki and T. L. Paoli, “Gain spectra in GaAs double-heterostructure injection lasers,” J. Appl. Phys. 46(3), 1299–1306 (1975). [CrossRef]

3

3. D. T. Cassidy, “Technique for measurement of the gain spectra of semiconductor diode lasers,” J. Appl. Phys. 56(11), 3096–3099 (1984). [CrossRef]

], Henry [4

4. C. H. Henry, R. A. Logan, and F. R. Merritt, “Measurement of gain and absorption spectra in AlGaAs buried heterostructure lasers,” J. Appl. Phys. 51(6), 3042–3050 (1980). [CrossRef]

], Oster et al [5

5. A. Oster, G. Erbert, and H. Wenzel, “Gain spectra measurements by a variable stripe length method with current injection,” Electron. Lett. 33(10), 864–866 (1997). [CrossRef]

, 6

6. A. Oster, F. Bugge, G. Erbert, and H. Wenzel, “Gain spectra measurement of strained and strain-compensated InGaAsP-AlGaAs laser structures for λ≅800 nm,” IEEE J. Sel. Top. Quantum Electron. 5, 631–636 (1999). [CrossRef]

], Thomson el al [7

7. J. D. Thomson, H. D. Summers, P. J. Hulyer, P. M. Smowton, and P. Blood, “Determination of single pass optical gain and internal loss using a multisection device,” Appl. Phys. Lett. 75(17), 2527–2529 (1999). [CrossRef]

12

12. Z. Mi, S. Fathpour, and P. Bhattacharya, “Measurement of modal gain in 1.1μm p-doped tunnel injection InGaAs/GaAs quantum dot laser heterostructure,” Electron. Lett. 41(23), 1282–1283 (2005). [CrossRef]

] and Troger [13

13. J. Troger, “Measurement of gain in pump diode lasers using a low-coherence source and synchronous detection,” J. Lightwave Technol. 21(12), 3441–3445 (2003). [CrossRef]

]. However, there are always several drawbacks in these methods. For instance, Hakki-Paoli’s method requires high spectral resolution of the measurement system [14

14. L. A. Lam Sin Cho, P. M. Smowton, and B. Thomas, “Spectral gain measurements for semiconductor laser diodes,” Proc. IEEE 137, 64–68 (1990).

], in order to resolve the longitudinal modes generated in F-P cavity. This increases the complexity in the experimental determination of the gain. Henry’s technique is based on the calculation of Fermi-level separation and absorption coefficient, and thus, it does not give the gain in absolute units so that the calibration is needed. Moreover, these two techniques are only suited for the small-signal gain measurement below the threshold point. In the Oster’s method, the use of different lengths of contact stripes in the amplified spontaneous emission (ASE) collection leads to the difficulty in ensuring a uniform collection efficiency of the spontaneous emission for every stripe so that the disparity with true gain spectra of the laser diode cannot be avoided. In the Thomson’s approach, the carrier diffusion between segments will inevitably lead to non-uniformity of the carrier distribution in each section, particularly in the case of high current density [15

15. S. Suchalkin, D. Westerfeld, G. Blenky, J. D. Bruno, J. Pham, F. Towner, and R. L. Tober, “Measurement of semiconductor laser gain by the segmented contact method under strong current spreading conditions,” IEEE J. Quantum Electron. 44(6), 561–566 (2008).

]. This will affect the gain measurement accuracy. In addition, the multi-section structure of the sample requires fairly precise etching processing, and thus increases the difficulty in experimental preparation. With Troger’s approach, the gain can be measured directly using the laser strip. However, the use of an additional light source will bring difficulty in achieving correct light coupling and signal collection between the light source and the diode.

2. Gain measurement principle

A diagram describing the amplified spontaneous emissions to be measured at dual facets of a laser diode is shown in Fig. 1
Fig. 1 Diagram of gain measurement model based on the ASE collected from dual facets.
, where the reflectance of the two facets are designed as R1 = 0 and R2 = R, respectively, and R can be any value of reflectivity which can be obtained by coating easily. R1 is designed as zero to avoid the intra-cavity light feedback at the facet. The ASE1 collected at R1-facet of the device consists of two ASE beams. One comes from the direct single-pass ASE beam to the R1-facet. The other is from the reflected part of the ASE beam by R2-facet.

G=1Lln(1R)IASE1IASE2RIASE2.
(6)

3. Experimental preparation and results

To analyze the HH and LH subband mixing situation in the valence band under different carrier densities and continuous operation condition with gain data, the theoretical gain curves of TE and TM polarizations are also calculated. The four-band k⋅p model including the valence-band mixing and the Lorentzian broadening is used. Since the injection current level is not too high for the continuous operation of the device concerning thermal effect influence on the gain measurement, the many-body Coulomb interaction is ignored in the gain modeling. The calculated material gains of TE and TM polarizations at room temperature are plotted in Fig. 5
Fig. 5 Calculated material gains with various carrier densities.
. The current densities of 10 A⋅cm−3 – 90 A⋅cm−3 correspond to the carrier concentrations of N = 1.45 - 4.6 × 1018 cm−3.

The calculated HH and LH subband distribution in the valence band is plotted in Fig. 6
Fig. 6 Calculated HH and LH subbands in the unstrained GaAs quantum well for a fixed carrier density.
. It can be clearly seen from Fig. 6 that there are three subbands of HH1, LH1 and HH2 in order, all of which are near to the top of the valence band for the unstrained structure. In comparison with the theoretical gain curves, the dual peaks in the TE gain curves are corresponding to the electron-hole recombination between the conduction band and the HH1, HH2 subbands, respectively, while the single TM gain peak mainly comes from the electron-hole recombination between the conduction band and the LH1 subband.

Since the gain generated at the long wavelength side is mainly from the electron-hole recombination between the conduction band and the HH1 subband around the wave vector kt = 0, the TE gain will be larger than the TM gain in this region. This can be interpreted by the transition matrix element (TME) theory [16

16. L. A. Coldren and S. W. Corzine, Diode Lasers and Photonic Integrated Circuits, 2nd edition (Wiley, 2012).

], in which the TME magnitudes of TE and TM polarizations are |M|TE2=|M|2/2 and |M|TM2=0, respectively, which are corresponding to the electron-hole recombination between the conduction band and the HH1 subband, where |M|2 is the fixed momentum matrix element and TME is associated with the recombination rate. At the short wavelength side, the TM gain may be larger than the TE gain, as the electron-hole recombination happens mainly between the conduction band and the LH1 subband. In this case, the TME values for TE and TM polarizations are changed to |M|TE2=|M|2/6 and |M|TM2=2|M|2/3, respectively.

4. Conclusions

Acknowledgments

The authors gratefully acknowledge the financial support of the National Natural Science Foundation of China (Grant No. 10974012) and for this work. F. Zhou acknowledges the support from the IUP Innovation Research Award.

References and links

1.

B. W. Hakki and T. L. Paoli, “Gain spectra in GaAs double-heterostructure injection lasers,” J. Appl. Phys. 46(3), 1299–1306 (1975). [CrossRef]

2.

B. W. Hakki and T. L. Paoli, “CW degradation at 300K of GaAs double-heterostructure junction lasers II. Electronic gain,” J. Appl. Phys. 44(9), 4113–4119 (1973). [CrossRef]

3.

D. T. Cassidy, “Technique for measurement of the gain spectra of semiconductor diode lasers,” J. Appl. Phys. 56(11), 3096–3099 (1984). [CrossRef]

4.

C. H. Henry, R. A. Logan, and F. R. Merritt, “Measurement of gain and absorption spectra in AlGaAs buried heterostructure lasers,” J. Appl. Phys. 51(6), 3042–3050 (1980). [CrossRef]

5.

A. Oster, G. Erbert, and H. Wenzel, “Gain spectra measurements by a variable stripe length method with current injection,” Electron. Lett. 33(10), 864–866 (1997). [CrossRef]

6.

A. Oster, F. Bugge, G. Erbert, and H. Wenzel, “Gain spectra measurement of strained and strain-compensated InGaAsP-AlGaAs laser structures for λ≅800 nm,” IEEE J. Sel. Top. Quantum Electron. 5, 631–636 (1999). [CrossRef]

7.

J. D. Thomson, H. D. Summers, P. J. Hulyer, P. M. Smowton, and P. Blood, “Determination of single pass optical gain and internal loss using a multisection device,” Appl. Phys. Lett. 75(17), 2527–2529 (1999). [CrossRef]

8.

J. D. Thomson, H. D. Summers, P. J. Hulyer, P. M. Smowton, and P. Blood, “Measurement of optical gain and Fermi level separation in semiconductor structures,” Proc. SPIE 3944, 201–208 (2000). [CrossRef]

9.

P. Blood, G. M. Lewis, P. M. Smowton, H. Summers, J. Thomson, and J. Lutti, “Characterization of semiconductor laser gain media by the segmented contact method,” IEEE J. Sel. Top. Quantum Electron. 9(5), 1275–1282 (2003). [CrossRef]

10.

G. M. Lewis, J. D. Thomson, P. M. Smowton, P. J. Hulyer, and P. Blood, “Gain characteristics of GaInIP quantum well laser structures,” Proc. SPIE 4651, 1–10 (2002). [CrossRef]

11.

G. M. Lewis, P. M. Smowton, P. Blood, G. Jones, and S. Bland, “Measurement of transverse electric and transverse magnetic spontaneous emission and gain in tensile strained GaInP laser diodes,” Appl. Phys. Lett. 80(19), 3488–3490 (2002). [CrossRef]

12.

Z. Mi, S. Fathpour, and P. Bhattacharya, “Measurement of modal gain in 1.1μm p-doped tunnel injection InGaAs/GaAs quantum dot laser heterostructure,” Electron. Lett. 41(23), 1282–1283 (2005). [CrossRef]

13.

J. Troger, “Measurement of gain in pump diode lasers using a low-coherence source and synchronous detection,” J. Lightwave Technol. 21(12), 3441–3445 (2003). [CrossRef]

14.

L. A. Lam Sin Cho, P. M. Smowton, and B. Thomas, “Spectral gain measurements for semiconductor laser diodes,” Proc. IEEE 137, 64–68 (1990).

15.

S. Suchalkin, D. Westerfeld, G. Blenky, J. D. Bruno, J. Pham, F. Towner, and R. L. Tober, “Measurement of semiconductor laser gain by the segmented contact method under strong current spreading conditions,” IEEE J. Quantum Electron. 44(6), 561–566 (2008).

16.

L. A. Coldren and S. W. Corzine, Diode Lasers and Photonic Integrated Circuits, 2nd edition (Wiley, 2012).

OCIS Codes
(250.5960) Optoelectronics : Semiconductor lasers
(250.5590) Optoelectronics : Quantum-well, -wire and -dot devices

ToC Category:
Optoelectronics

History
Original Manuscript: February 13, 2013
Revised Manuscript: April 1, 2013
Manuscript Accepted: April 2, 2013
Published: April 19, 2013

Citation
M-L Ma, J Wu, Y-Q Ning, F Zhou, M Yang, X Zhang, J Zhang, and G-Y Shang, "Measurement of gain characteristics of semiconductor lasers by amplified spontaneous emissions from dual facets," Opt. Express 21, 10335-10341 (2013)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-21-8-10335


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References

  1. B. W. Hakki and T. L. Paoli, “Gain spectra in GaAs double-heterostructure injection lasers,” J. Appl. Phys.46(3), 1299–1306 (1975). [CrossRef]
  2. B. W. Hakki and T. L. Paoli, “CW degradation at 300K of GaAs double-heterostructure junction lasers II. Electronic gain,” J. Appl. Phys.44(9), 4113–4119 (1973). [CrossRef]
  3. D. T. Cassidy, “Technique for measurement of the gain spectra of semiconductor diode lasers,” J. Appl. Phys.56(11), 3096–3099 (1984). [CrossRef]
  4. C. H. Henry, R. A. Logan, and F. R. Merritt, “Measurement of gain and absorption spectra in AlGaAs buried heterostructure lasers,” J. Appl. Phys.51(6), 3042–3050 (1980). [CrossRef]
  5. A. Oster, G. Erbert, and H. Wenzel, “Gain spectra measurements by a variable stripe length method with current injection,” Electron. Lett.33(10), 864–866 (1997). [CrossRef]
  6. A. Oster, F. Bugge, G. Erbert, and H. Wenzel, “Gain spectra measurement of strained and strain-compensated InGaAsP-AlGaAs laser structures for λ≅800 nm,” IEEE J. Sel. Top. Quantum Electron.5, 631–636 (1999). [CrossRef]
  7. J. D. Thomson, H. D. Summers, P. J. Hulyer, P. M. Smowton, and P. Blood, “Determination of single pass optical gain and internal loss using a multisection device,” Appl. Phys. Lett.75(17), 2527–2529 (1999). [CrossRef]
  8. J. D. Thomson, H. D. Summers, P. J. Hulyer, P. M. Smowton, and P. Blood, “Measurement of optical gain and Fermi level separation in semiconductor structures,” Proc. SPIE3944, 201–208 (2000). [CrossRef]
  9. P. Blood, G. M. Lewis, P. M. Smowton, H. Summers, J. Thomson, and J. Lutti, “Characterization of semiconductor laser gain media by the segmented contact method,” IEEE J. Sel. Top. Quantum Electron.9(5), 1275–1282 (2003). [CrossRef]
  10. G. M. Lewis, J. D. Thomson, P. M. Smowton, P. J. Hulyer, and P. Blood, “Gain characteristics of GaInIP quantum well laser structures,” Proc. SPIE4651, 1–10 (2002). [CrossRef]
  11. G. M. Lewis, P. M. Smowton, P. Blood, G. Jones, and S. Bland, “Measurement of transverse electric and transverse magnetic spontaneous emission and gain in tensile strained GaInP laser diodes,” Appl. Phys. Lett.80(19), 3488–3490 (2002). [CrossRef]
  12. Z. Mi, S. Fathpour, and P. Bhattacharya, “Measurement of modal gain in 1.1μm p-doped tunnel injection InGaAs/GaAs quantum dot laser heterostructure,” Electron. Lett.41(23), 1282–1283 (2005). [CrossRef]
  13. J. Troger, “Measurement of gain in pump diode lasers using a low-coherence source and synchronous detection,” J. Lightwave Technol.21(12), 3441–3445 (2003). [CrossRef]
  14. L. A. Lam Sin Cho, P. M. Smowton, and B. Thomas, “Spectral gain measurements for semiconductor laser diodes,” Proc. IEEE137, 64–68 (1990).
  15. S. Suchalkin, D. Westerfeld, G. Blenky, J. D. Bruno, J. Pham, F. Towner, and R. L. Tober, “Measurement of semiconductor laser gain by the segmented contact method under strong current spreading conditions,” IEEE J. Quantum Electron.44(6), 561–566 (2008).
  16. L. A. Coldren and S. W. Corzine, Diode Lasers and Photonic Integrated Circuits, 2nd edition (Wiley, 2012).

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