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NKNU phys. Master Thesis

NKNU phys. Master Thesis. The measurement and study of femto-second gain dynamics of GaAs single quantum well semiconductor laser amplifiers. 國立彰化師大物理系博士班入學口試. Contents. Chap.1 Introduction Chap.2 GaAs SLA Chap.3 Theory Chap.4 Laser system Chap.5 Gain dynamics Chap.6 Summary

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NKNU phys. Master Thesis

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  1. NKNU phys. Master Thesis The measurement and study of femto-second gain dynamics of GaAs single quantum well semiconductor laser amplifiers 國立彰化師大物理系博士班入學口試

  2. Contents • Chap.1 Introduction • Chap.2 GaAs SLA • Chap.3 Theory • Chap.4 Laser system • Chap.5 Gain dynamics • Chap.6 Summary • Appendix

  3. SLA advantages Small volume<500 micro-meter Short response time<200ps High gain>30dB Broad band>5T Hz Support: NSC87-2112-M-017-001 NSC87-2112-M-017-002 Follow up:NSC87-2112-M-017-003 Advantages & support

  4. 1.1 Background 1.2 Study focus Chap.1 Introduction

  5. Experiment ~1980:linear gain 1980~fs laser Nonlinear gain MIT: ps pump probe technique & TDI UC Davis: fs Nonlinear index ~MIT Theory 1989:AT&T 1992:UC Davis 1992:TFL(Sweden) Domestic researches 1.1 Background

  6. 1.2 Study focus

  7. 2.1 Introduction 2.2 SLD830 2.3 Mounting system and circuit box 2.4 SLD830 measurement Chap.2 GaAs SLA

  8. 2.1 Introduction

  9. GaAs Direct band-gap Gain: LD,LED & SLA Absorption: optical detector: Photo Diode SLD USA Sarnoff Inc. Single Quantum Well Double Hetero-junction Structure Peak wavelength: 825nm Striped angle:5 deg. Active layer:0.08 micro-meter P-side down 830 <GaAs band-gap wavelength=870nm 2.2 SLD830

  10. Manufactory LI & Spectrum

  11. Structure

  12. Photos ~bird’s eye & side

  13. 2.3 Mounting system &circuit box

  14. (a)樣品裝載； (b)頂住的螺絲 (c)SMA接頭； (d)基座； (e)基座裝載； (f)絕緣夾層； (g)載台支撐棒； (h)圓形壓版。

  15. 2.4 SLD830 measurement

  16. VI

  17. LI

  18. Spectrum ~TE & TM=1:10

  19. Bandwidth=2nm

  20. Transparent current

  21. 25mA

  22. Gain curve

  23. 3.1 Introduction 3.2 Pump probe technique 3.3 Semi-phenomenological model Chap.3 Theory Models

  24. 3.1 Introduction In semiconductors: two level energy model+ energy conservation law + momentum conservation law+ boundary conditions Where: mc: electron effective mass in conduction band mv: hole effective mass in valance band Ec: bottom energy of conduction band Ev: top energy of valance band Eg( energy gap)=Ec-Ev

  25. Optical joint density of states Fermi Golden Rule Lorentzian line-shape function Well known equations

  26. R: index，I: gain

  27. where: h(t): resonance function G(2)(t):convolution of h(t) S(τ): auto-correlation function of G(2)(t) 3.2 Pump probe technique

  28. 1989 AT&T G.P. Agrawal where: Vg: group velocity g(N): gain α: Line-width Enhancement Factor 3.3 Semi-phenomenological model

  29. 4.1 Introduction 4.2 Pumping source:NdYVO4 Laser 4.3 Ultra-short mode-locking Ti: sapphire Laser 4.4 Pulse-width and bandwidth Chap.4 Laser System

  30. Ultra fast Mode-locking fs pulse laser 4.1 Introduction

  31. Power>5W Wavelength: 532nm Quasi single frequency:<1nm Spot size:2.25mm Beam waist:1/e^2，beam divergence<0.5mrad Polarization: vertical: parallel>100:1 4.2 Pumping source:NdYVO4 Laser

  32. Coherent Verdi

  33. Wavelength tunable:730~850nm Repetition rate:76MHz CW power:800mW Mode-locking power:600mW Peak power:50KW Spot size:0.8mm Full angle divergence:1.5mrad Polarization:TEM00,p polarization 4.3 Ultra-short mode-locking Ti: sapphire Laser

  34. Coherent Mira

  35. 4.4 Pulse-width and bandwidth

  36. Auto-correlator Femto-chrome FR-103XL

  37. Pulse-width=110fs un-chirped

  38. Line-width=10nm transform limited OSA:HP 71451B

  39. 5.1 Introduction 5.2 Pump probe system 5.3 Gain dynamics 5.4 Experiment result Chap.5 Gain Dynamics

  40. Pump probe 3 factors =pump beam + probe beam +time delay Two beams pump probe/three beams Parallel polarization/orthogonal polarization Refraction /reflection 5.1 Introduction

  41. 5.2 Pump probe system • System requirements • Experiment sketch

  42. Pump & probe power tunable Pump & probe polarization tunable Wavelength tunable SLA driving current tunable Time delay tunable Alignment requirement Fine tuning and double check System requirements

  43. Experiment sketch

  44. Data acquisition &instrument control

  45. 5.3 Gain dynamics fixed alternative

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