Download OPTICAL MODELING

The design of a complete system level modeling and
simulation tool for optical micro-systems is the
focus of our research . We use a rigorous optical
modeling technique based on the rigorous Scalar
Rayleigh-Sommerfeld formulation, which is
efficiently solved with an angular spectrum
approach. Our current research involves a semivector analysis which is applied in cases where the
boundary conditions have to be explicitly modeled .
In a related area of research, we are using our
optical modeling technique to support the challenge
of automated alignment and packaging of complex
optical micro-systems.
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ELECTRONICS
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OPTICS
TELECOMMUNICATIONS
http://www.
usitt.ecs.so
ton.ac.uk
Switches,
Attenuators,
Modulators
BELL-Labs
MICROMECHANICS
SENSING
Thick-Film PZT Sensing Element
LUCENT
IMAGING
OPTICAL COMPUTING
UCLA –Integrated Free-Space Optical Disk
Pickup Head
Texas Instruments-DMD
System Level
• Ensemble of component behavioral
models.
• Fast solvers at component/behavior
System Modeling
System Performance
level.
• Domain specific signal propagation
models.
• Global discrete event dataflow.
Behavioral Level
Circuit Modeling
Reduced Order-ODE
Ensemble performance measures:
• BER
• Optical/electrical crosstalk.
• Packaging/alignment tolerances.
• Thermal effects.
Device Level
Device Modeling
3D/EM
Ray Propagation
- Direction, position and angles
Gaussian Propagation
- 9 scalar parameters(z0,x,y,z,etc..)
- Fast simulation (no integration)
- Limited diffraction modeling
Scalar Optics
- 2D complex wave front
- Propagation by summation of wave
fronts
Vector Analysis
- Intensive computation, Boundary
Element
RayleighSommerfeld &
Fresnel-Kirchoff
Full Wave
Solutions
Z >> λ
Fresnel
(Near Field)
Z >>
Fraunhofer
(Far field)
Z >>
Scalar Approximations
Vector
Solutions
Wave front
-Parabolic
Wave front
-Spherical
Wave front
-Planar
Micro-Systems
850nm
966um
z
4.66mm
Example: 50 um Aperture, 200 um Observation, λ=850 nm
SCALAR DIFFRACTION-RAYLEIGH SOMMERFELD FORMULATION:
• Diffractive component >>λ
• Distance to observation plane >>λ
z
U 2( x, y) 
j
e jkr
 U1( , ) r 2  

IMPLEMENTATION:
x
y

• Huygens- Fresnel Principle
r
z
• Direct Integration
- Computation Order: O(N4)
•Angular Spectrum Approach
U1(,)
- Computation Order: O(N2LogN)
U2(x,y)
Input Complex
Wave front
Spatial Domain
Free Space Propagation
Fourier Domain
Output Complex
Wave front
Spatial Domain
• Decompose Spherical wave front into angled
plane waves using Fast Fourier Transform.
• Multiply with Free Space Transfer function.
• Sum Plane waves into Spherical Wave
Function with Inverse Fast Fourier Transform.
• Computational order (N2LogN).
Spatial Frequencies
Observation
Plane
Aperture Plane
Free Space Propagation
Example: 100X100 points, λ=850nm, spot size=20um, z=300um
Tilt in x
Offset in Y
Example: 100X100 points, λ=850nm, spot size=20um, z=300um
f
VCSEL
2f
f
THIN REFRACTIVE LENS
DETECTOR
REFRACTIVE LENS
King et al. 1996
Input
Output
Z=300um
Example: 100X100 points, λ=850nm, spot size=20um, z=300um, focal
length=100um
UCLA- Fresnel Lens
f
2f
f
FRESNEL LENS
Input
Output
Z=300um
Example: 100X100 points, λ=850nm, spot size=20um, z=300um, focal
length=100um
Transition of Scalar Wave theory to Semi-Vector
theory in cases where boundary conditions have
to be taken into consideration.
An Optical System that alters the
Polarization of a plane wave
Example:
Reflection and
Refraction of a
TEM wave
Reflected
Refracted
Multi Thin-film stack
Incident
A Complex wave
incident at a
planar interface
with n1=1,
n2=1.5,z1=300um,
z2=300um,z3=300
um.
R3
T3 n3
R2
T2 n2
R1
T1
n1
In a related area of research, we propose:
OPTICAL MODELING:
Efficient Rayleigh- Sommerfeld Scalar
and Semi-Vector Modeling.
CONTROL ALGORITHM:
Model Predictive control.
A Planar Light wave
Structure
EMPLOY:
Off -the-shelf semiconductor and other
automation assembly equipment.
BENEFITS:
High Performance, Low cost,
Increased Productivity.
www.bonders.com
•Simulation performed using
system level optical CAD tool
•Uses Rayleigh-Sommerfeld
scalar modeling
•Set initial position
(i.e., feed forward)
•Enable Input Source
for power testing
Reference Input
Feed-forward
Controller
+
-
Feedback
Controller
Motor
Power Efficiency
Vs.
Displacement
Output
Power Sensing
Element
•Determine errors between
expected maximum power
and measured
•Fine tune position for
fabrication misalignments
•Detect Power
www.bonders.com
Current Solution:
Proposed Solution:
Compares optical power
with neighboring optical
power, until maximum is
reached. In this example,
takes 50 time steps.
Simulate system to find
initial position, then fine
tune result. Alignment
reached quickly. In this
example, takes 3 time
steps.
Optical Intensity Profile
Fiber-Array
Coupling
Current Solution:
Proposed Solution:
Hill climbing method gets caught
in a local minimum of intensity
distribution.
With simulation, we feed forward
our control algorithm to the ideal
initial placement.
Achievement of speed of Fraunhofer
approximation, with the accuracy of RayleighSommerfeld formulation.
A Semi-Vector technique is employed to support
boundary conditions.
More System Level Simulations and Validations.
Advanced Modeling of MEMS and Grating
Devices.
Error Prediction.