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Quantum-Dot Lasers

Quantum-Dot Lasers. Nanoelectronics term project R91543013 徐維良 指導教授 : 劉致為. Outline. 半導體雷射與 Quantum dot laser Quantum dot laser 的製造 Quantum dot laser 的特色 高能的 Quantum dot laser 1.3 µ m Quantum Dot Lasers 結論. 半導體雷射. LASER:Light Amplification by Stimulated Emission of Radiation 必要的元件 :

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Quantum-Dot Lasers

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  1. Quantum-Dot Lasers Nanoelectronics term project R91543013 徐維良 指導教授:劉致為

  2. Outline • 半導體雷射與Quantum dot laser • Quantum dot laser的製造 • Quantum dot laser的特色 • 高能的Quantum dot laser • 1.3 µm Quantum Dot Lasers • 結論

  3. 半導體雷射 LASER:Light Amplification by Stimulated Emission of Radiation 必要的元件: --Gain medium --Optical feedback • 利用Quantum dot transition 的放射結合來放大. • •Pumping over p-n junction by current injection • 利用水晶面來反射以共振

  4. 增益與尺寸

  5. Quantum Dot的好處 Discrete energy level : high density of states no temperature dependence

  6. Quantum Dot的好處 reduced diffusion → no diffusion to surfaces reduced active volume → low absorption, low inversion densities refractive index decoupled from carrier density → no chirp

  7. Quantum dot laser的製造 MBE-Growth Integration of Quantum dot layer into the active zone of a semiconductor laser Dot density>10^10cm^-2

  8. 改良Carrier Confinement Quantum dot laser的active region對於thermal losses較敏感 • SSLs as 布拉格反射體 • 改良Carrier Confinement

  9. 改良Carrier Confinement 不同區域的short period superlattices 之結合 mini bandgap 的部分重合導致effective barrier height的增加

  10. 溫度與Quantum dot laser Reduced wavelength shift: QW: 0.33 nm/K QDots: 0.17 - 0.19 nm/K Operation temperature > 210 °C

  11. Quantum dot laser 之增益 • About 3 times broader gain spectrum due to dot size • distribution • •Much larger tuning range for wavelength tuning of DFB • lasers

  12. Single mode Emitting Quantum dot lasers • 使用E-Beam製造 • • Wavelength selection by grating • periode (SMSR = 52 dB) • • Ith < 20 mA for all periods • (.λ = 33 nm)

  13. 溫度穩定性 • Stable single mode emission • No mode hopping • Single mode operation over • 194K temperature range • 三倍大的頻寬 • 溫度飄移少一倍

  14. Quantum Dot 與Quantum Well • Reduced threshold current density for L > 2.5 mm (cross over) • Lower optical confinement for QDots, but inversion condition is relaxed

  15. Material Gain of Q-Dot and QW-Laser

  16. 波長對溫度敏感度 Quantum dot laser有較低的溫度敏感度 △λ/ △ T = 0.35 nm/K for QWLs = 0.23 nm/K for QDLs

  17. 高能的Quantum dot laser • 2 mm × 100 µm broad area laser • Record value of 4 W cw output power • Wall plug efficiency > 50 % at 1 W

  18. 高能的Quantum dot laser • Emission by fundamental mode • High temperature stability • Low wavelength shift (for QWs 50% higher)

  19. 高能的Quantum dot laser • 在20°C 與 80°C 的區域中，每增加一瓦的能量，只有多百分之二十的電流 • 高的characteristic temperature • T= 110 K up to 110 °C

  20. 1.3 µm Quantum Dot Lasers • 替代昂貴的InP-based material system • Growth on GaAs substrates, --便宜、 大的WAFER面積(6", 8") • special dot 優點 --low threshold density --broad gain function --low temperature sensitivity

  21. InAs/GaInAs Quantum Dots • InAs embedded in GaInAs buffer layers • – Room temperature emission at 1.3 µm • – High quantum dot density • • Growth rate: r(GaAs) = 1 µm/h • r(InAs) = 140 to 260 nm/h • • Growth temperature: T = 510 °C

  22. 1.3 µm Quantum Dots

  23. 1.3 µm Quantum Dots • High dot densities for InAs on GaInAs • 35 - 40 meV line width • 60 meV level distance • Longer wavelength at higher In content

  24. 1.3 µm Quantum Dot Laser • 6 InAs/GaInAs Q-Dot layers with 50 nm GaAs spacers • • 650 nm cavity width • • GRINSCH with SSL structure • • 1,6 µm Al0.4Ga0.6As • cladding layers

  25. 1.3 µm Quantum Dot Laser •Laser emission by fundamental mode • 800 µm resonator length possible without mirror coating

  26. Threshold Current Density • • For 6 Q-Dot layers threshold doubles but 800 µm device length • possible • For 3 Q-Dot layers low threshold current density (100 - 200 • A/cm2)but limitation to about 2.5 mm resonator length

  27. Modal Gain of Quantum dot Layers • L = shortest resonator length at which laser operation is still possible on the ground state • About 2 - 3 cm-1 modal gain per dot layer • Best results with 6 dot layers achieved

  28. Tuning Range of QDot-Lasers • Linear correlation of grating period and emission avelength – Tuning range > 35 nm – Basic device properties are almost identical over the whole tuning range → A further extension of the tuning range to longer and shorter wavelengths should be possible

  29. 高頻特性 • Large modulation bandwidth for 800 µm long HR/HR coated device • 3dB bandwidth thermally limited

  30. 結論 • Quantum dot laser 的好處 –低很多的 inversion carrier density (低 threshold current) –對溫度較不敏感 –有大的頻寬 – low chirp

  31. 結論 •已實體化的 Quantum dot laser – 980 nm single mode emitting laser with extremely high temperature stability (Top = 15 °C - 210 °C) – 980 nm high power lasers (4 W cw output power, > 50% wall plug eff.) – 1.3 µm laser with high device performance (Ith = 4.4 mA, Top. > 150°C)

  32. Reference http://www.compoundsemiconductor.net/articles/news/6/3/21/1 http://fibers.org/articles/fs/6/12/3/1 http://fibers.org/articles/fs/6/11/3/1 http://www.ee.leeds.ac.uk/nanomsc/presentations/module2presentation.htm http://www.indianpatents.org.in/ach/quant.htm http://newton.ex.ac.uk/aip/physnews.595.html http://www.aip.org/enews/physnews/2003/ http://www.elec.gla.ac.uk/groups/nanospec/dotlaser.html http://www.shef.ac.uk/uni/academic/N-Q/phys/research/semic/qdresgroup.html#Laser

  33. Reference http://optics.org/articles/ole/7/8/2/1 http://feynman.stanford.edu/Html-CQED/sqdl.html http://www.hinduonnet.com/thehindu/2001/09/13/stories/08130006.htm http://www.phy.ncu.edu.tw/so/Chinese/Quantum%20Dots/Search%20subject1.htm http://www.sciam.com.tw/read/readshow.asp?FDocNo=121&DocNo=191 L.A.Coldren and S.W.Corzine, Diode Lasers and Photonic Integrated Circuits (Wiley, New York 1995). M.Asada, Y.Miyamoto, and Y.Suematsu, IEEE J.Quantum Electron. QE-22, 1915(1986).

  34. Reference • R. P. Mirin, J. P. Ibbetson, K. Nishi, A. C. Gossard, and J. E. Bowers, Appl. Phys. Lett.67, 3795 (1995). • K. Nishi, H. Saito, S. Sugou, and J.-S. Lee, Appl. Phys. Lett. 74, 1111 (1999). • V. M. Ustinov, N. A. Maleev, A. E. Zhukov, A. R. Kovsh, A. Yu. Egorov, A. V.Lunev, B. V. Volovik, I. L. Krestnikov, Yu. G. Musikhin, N. A. Bert, P. S. Kop’ev, andZh. I. Alferov, N. N. Ledentsov, and D. Bimberg, Appl. Phys. Lett. 74, 2815 (1999). • D. L. Huffaker, G. Park, Z. Zou, O. B. Shchekin, and D. G. Deppe, Appl. Phys. Lett.73, 2564 (1998). • Y.M. Shernyakov, D.A. Bedarev, E.Y. Kondrateva, P.S. Kopev, A.R. Kovsh, N.A. Maleev, M.V. Maximov, S.S. Mikhrin, A.F. Tsatsulnikov, V.M. Ustinov, B.V. Volovik,A.E. Zhukov, Z.I. Alferov,N.N.Ledentsov, D. Bimberg, Electron. Lett, 35, 898, (1999) • G. T. Liu, A. Stintz, H. Li, K. J. Malloy, and L. F. Lester, Electron. Lett. 35, 1163(1999). • L. F. Lester, A. Stintz, H. Li, T. C. Newell, E. A. Pease, B. A. Fuchs, and K. J. Malloy,IEEE Photon. Technol. Lett. 11, 931 (1999).

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