Intoduction to VCSEL Device Simulation

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Intoduction to VCSEL Device Simulation

• Mou Zongying 07-06-2004

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VCSEL Device Simulation

• Introduction
• Basic concepts of Laser and semiconductor
• Physical model of VCSEL device
• Computing optical mode
• Numerical simulation
• Simulation results

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Introdction

• VCSEL
• vertical-cavity surface-emitting laser
  (semiconductor laser device, diode laser)
• Telecomunications, Pumping source
• Wave length from infrared to visible
• etched mesa VCSEL 980nm
• Buried tunnel junction(BTJ) VCSEL
  1300nm,1550nm
• Material
• ALGaAs(GaAs),InGaAsP(InP)
• Simulators are needed to explore the design
  parameter for an optimum solutionlow cost and
  short time for a design cycle

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Basic Concepts of Laser

• Laser

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Requirements for Laser Action

• Population inversion

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Basic Concepts of Semiconductor

• There are three types of conductors
• . Insulaters
• .Metals
• .Semicondctors

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Energy Band for Solid

• Metals
• . Overlapping energy bands or vary small gap
• . Electrons in conduction band
• Semiconductors
• . Small energy gap lt2ev
• . Some electrons in conduction band
• Insulators
• . Large energy gap
• . No electrons in conduction band

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Physical Model of VCSEL

• Diode laser devices history
• Physical Model of VCSEl
• Schematic of two kinds of VCSEL
• .Etched Mesa
• .BTJ
• Maxwells equation
• Laser device simulation

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Diode Laser Devices

• First working device appeared in 1962, at low
  temperature
• Structure containing several semiconductor layers
  In 1969, at room temperature
• After 1990, employed BTJ which causes a
  transverse waveguiding--stable transverse mode
  profile and small threshold current

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Physical Model of VCSEL

• Time Dependent Model (Finite Difference Time
  Domain) in 1995
• Stationay Model (Finite Difference Method) in
  1995
• Microscopic VCSEL Model in 1998
• Isothermal Electric model in 1999
• Method of Lines in 2001

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Etched Mesa VCSEL
Schematic Etched Mesa VCSEL. DBR( distributed
Bragg Resonator)
Etched Mesa VCSEL(electron micrograph)
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Etched Mesa VCSEL
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BTJ VCSEL

• Schematic Buried Tunnel Junction VCSEL

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Etched Mesa and BTJ VCSEL

• Schematic cross section of two types of VCSEL

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Maxwells Equation

• Maxwells eq. and material eq.

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Maxwell wave equation

• for J0

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Maxwell wave equation
Separate
Eigenvalue problem
Frequency
Normalization
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Laser Device Simulation

• Dielectric fuction

Mechanism . Direct interband absorption .
Indirect interband absorption . Free carrier
absorption . Interconduction band and
intervalence band absorption
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Laser Device Simulation

• Photon rate eq.

Where Sk is the photon number Rk is
spontaneous emmission wk is the net modal
rate change
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Computing Optical Mode

• Open Cavity

. Only the innerboundary Structure determines the
optical mode . Outerboundary is an absorber
(no backscattering)
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Computing Optical Mode

• Variational function

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Computing Optical Mode

• Rotation symmetric

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Computing Optical Mode

• Variational function for axi-symmetric case

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Computing Optical Mode

• Boundary condition

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Numerical Simulation

• Jacobi-Davidson QZ iteration method
• Biconjugate gradient stabilished method
  (BiCGstab) is used to solve Jacobi correction
  equation and speed up the convergence
• Software LUM12 mode solver package

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Simulation Result

• The intensity of ?k(z)
• for the fundermental
• longitudinal VCSEL mode
• (Etched Mesa)

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Simulation Result

• Foundmental mode (BTJ)

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Simulation Result

• Higher mode (BTJ)

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3D Numerical Simulation

• Edge finite elements for solving 3D-Maxwell
  equation
• . Shape function are vectors
• . Unknows now along the edge
• . Natural elements for Maxwells equation
• . Restriction domain has to be convex

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Thanks for your attendance!