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skai · 发表于 2003-5-27 16:56:00

请教：
  在ASAP中，如果入射是高斯光线，为什么在使用GAUSSIAN命令后，当光线追迹到透镜或者光纤时，还要使用DECOMPOSE DIRECTION，它的具体含义是什么？因为下面的程序先用GAUSSIAN命令定义了高斯光线，然后接着就使用DECOMPOSE DIRECTION命令。如果我不使用DECOMPOSE DIRECTION命令，直接就Trace可不可以呢？
  另外，PARABASAL命令有什么用？
  您能把下面的程序帮我解释一下吗？谢谢！
!!++
!! BPMLASER_COUPLING.INR
!! Title: Laser Coupling with BPM
!! Category: Isolated Command
!! Keywords: BPM, FIELD, COUPLE, DECOMPOSE
!! Description: This file demonstrates the use of
!! ASAP for calculating the coupling efficiency
!! of a laser diode to a single-mode fiber. It uses
!! gaussian beams to propagate from the laser, through
!! a ball lens, to just before the fiber’s entrance.
!! It propagates through the entrance and a short distance
!! along the fiber using the beam propagation method (BPM).
!! Edit History (latest first)
!! 12/19/2002 - cp - modified format, added comments
!! 12/18/2000 - DCS - modified to use BPM, and name changed.
!! 03/27/2000 - cp - modified format; added description
!! 11/01/1999 - js - creation
!!--

!! Initialization commands
SYSTEM NEW !! Clear out any existing geometry
RESET !! Clear out any existing sources/rays
UNITS MICRONS !! Set system units
FRESNEL AVERAGE
PI=ACOS(-1)
!! Define geometry parameters
DLENS=300 !! Lens diameter
RLENS=DLENS/2  !! Lens Radius
D1=43    !! Source-to-lens distance
D2=290    !! Lens-to-fiber distance
!! Fiber parameters
WAVEL=1.55 !! Wavelength (in microns)
NCORE=1.456427 !! Core index of refraction
NCLAD=1.449679 !! Cladding index of refraction
RCORE=5.9/2 !! Core radius
RCLAD=100/2 !! Cladding radius
ROUT=125/2 !! Outer (absorbing) layer radius
OUTAB=0.1 !! Absorption coefficient for absorbing layer
!! Misc parameters
RES=300 !! Vertical resolution for BPM calculation
EPS=0.01 !! = epsilon (a small distance)
PROP_DIST=200 !! Distance to propagate in the fiber
NPLANES=20  !! Number of planes to save the field at in the fiber
!! Calculated parameters
WINDO=ROUT+EPS       !! Window size for BPM calculation
FSTART=D1+DLENS+D2+EPS    !! Location of fiber’s entrance
FEND=D1+DLENS+D2+EPS+PROP_DIST !! End of fiber location
!! Calculate (and display) the numerical aperture and V number
!! of the fiber...
NA=SQRT(NCORE*NCORE-NCLAD*NCLAD)
VN=2*PI*RCORE*NA/WAVEL
$SCR 3 !!
Fiber characteristics:
Numerical Aperture = \NA.3\
V Number = \VN.3\
!! Set the wavelength
WAVELENGTH (WAVEL) MICRONS
!! Define functions to represent the step-index fiber’s index profile...
$FCN FIBER  NCORE+(NCLAD-NCORE)*STEP(SQRT(_1*_1+_2*_2)-RCORE)
$FCN OUT_CLAD STEP(SQRT(_1*_1+_2*_2)-RCLAD)
FUNCTION
USERFUNC 0 0 0 FIBER
USERFUNC 0 0 0 OUT_CLAD
!! Define media
MEDIA
1 GRIN 1 2 ABSORB (OUTAB) 2 1 ’FIBER’
2.1417 ’NBALL’
!! Define the ball lens at Z=D1+RLENS
SURFACE
ELLIPSOID 3@(RLENS) 0 0 (D1+RLENS)
OBJECT ’BALL_LENS’
INTERFACE COATING +BARE AIR NBALL
REDEFINE COLOR 1
!! Define the detector at D1+DLENS+D2
!! Make it large enough to collect all rays of possible interest. The tails
!! of some may still contribute inside the fiber’s window.
SURFACE
PLANE Z (D1+DLENS+D2) ELLIPSE 2@(RLENS)
OBJECT ’DETECTOR’
INTERFACE 0 0 AIR AIR
REDEFINE COLOR 3
!! Define the fiber’s face and outer edge
SURFACE
TUBE Z (FSTART) 2@(ROUT) (FEND) 2@(ROUT) 0 0
OBJECT ’FIBER.EDGE’
INTERFACE 0 1 AIR FIBER
REDEFINE COLOR 4
SURFACE
PLANE Z (FSTART) ELLIP (ROUT)
OBJECT ’FIBER.FACE’
INTERFACE 0 1 AIR FIBER
REDEFINE COLOR 4
!! Define the source
WIDTHS 1.6
PARABASAL 4
BEAMS COHERENT DIFFRACT
W0X=1.50*0.886 !! convert to ASAP width def
W0Y=0.65*0.886 !! convert to ASAP width def
GAUSSIAN Z 0 0 0 1 1 0 0 (W0X) (W0Y)
WINDOW X -2@4 Y -2@2
PIXELS 201
FIELD ENERGY 0
!! Decompose directionally due to very small waist
RAYS 0  !! Delete old rays before making new
FTSIZE 9 !! set fourier transform size to 512 (= 2^9)
DECOMPOSE DIRECTION 0.1 45
!! Look at the field just in front
!! of the ball lens, and grab the
!! total integrated flux from the
!! console window, saving it to a
!! the variable named E0. Note that
!! the beams were not traced up to
!! this place. ASAP can compute the
!! field at any Z position specified
!! as long as there are no intervening
!! optical elements. D1 is the location
!! of the ball-lens vertex.
!! This is not part of the coupling
!! Calculation, but used to determine
!! the total energy losses throughout
!! the system due to various causes.
WINDOW Y -56 56 X -56 56
FIELD ENERGY (D1-EPS)
$CLEAR
DISPLAY
$GRAB ’Integral’ E0
PICTURE
GRAPH
TRANSPOSE
GRAPH
RETURN
WINDOW Y Z
PLOT FACETS 9 9 OVERLAY
!! Trace rays through the ball lens
TRACE PLOT 5 COLOR 2
CONSIDER ONLY DETECTOR
PIXELS (RES)
WINDOW X -2@(WINDO) Y -2@(WINDO)
FIELD ENERGY (D1+DLENS+D2)
$COPY 29 FIBER_INPUT_29.DIS
!! Grab the resulting energy from the
!! console window and save it to E1
!! This shows other losses, including
!! Fresnel.
$CLEAR
DISPLAY
$GRAB ’Integral’ E1
RETURN
!! Next propagate the input into, and along, the fiber using BPM method.
!! We’ll use the field calculated above as our input.
CONSIDER ONLY FIBER.?
FIELD FIBER_INPUT_29.DIS ENERGY (D1+DLENS+D2) (FEND) (NPLANES) BC 1 1
$COPY 9 FIBER_PROP.DIS
$COPY 29 FIBER_PROP_29.DIS
!! View the results in 3d viewer
$VIEW
VIEW FIBER_PROP.DIS
!! Next define the fiber mode as if it
!! were a new source, and compute the
!! overlap with FIELD COUPLE.
RAYS 0 !! delete all previous rays/sources
IMMERSE FIBER
RAYSET Z (FEND); 0 0 1 2@(RCORE) -FIBR (VN)
SOURCE DIR Z
FIELD ENERGY (FEND)
!! The expected fiber mode is now in the BRO029.DAT (field components)
!! and BRO009.DAT (energy) files. Next, couple the results of
!! our propagation to this mode.
$CLEAR
!! The following command line is from Syntax #2 (BPM mode) of the FIELD command.
!! Since no distance is specified for propagating the named field, it defaults
!! to 0. In this case, ASAP simply couples the named file to the field
!! already in the BRO029.DAT file (from the previous FIELD ENERGY command).
FIELD FIBER_PROP_29.DIS ENERGY COUPLE !! The mode in BRO029.DAT is then rescaled
                  !! by the projection of the named field
                  !! onto it. The corresponding rescaled
                  !! energy profile is written to BRO009.DAT.
!! Grab total energy that made it into the fiber mode
$CLEAR
DISPLAY
$GRAB ’Integral’ E2 !! This is the overlap integral calculated by
         !! the previous FIELD COUPLE
RETURN
!! Calculate and display the overall coupling efficiency
OCE=(E2/E0)*100
$SCR 5
Energy:
at source       = \E0.3\
just before entering fiber = \E1.3\
coupled to fiber mode = \E2.3\
Overall Efficiency = \OCE.1\%
RETURN

Photonics · 发表于 2003-5-27 22:30:00

呵呵
您的问题说来话长
总之ASAP模拟COHERENT的GAUSSIAN BEAM是用GAUSSIAN BEAM DECOMPSITION演算方式
您可以在说明书上找到说明
它是将光线分为主光线和包围的子光线来模拟GAUSSIAN BEAM
不可直接TRACE
因为这已经不用RAY TRACE的方法演算了
至于这个例子,这是ASAP的一个例子,要全部解释,就饶了我吧
太多了

skai · 发表于 2003-5-28 00:29:00

将光线分为主光线和包围的子光线是什么意思？
DECOMPOSE DIRECTION的参数代表什么呢？

Photonics · 发表于 2003-5-28 00:53:00

GAUSSIAN BEAM是个光束
它不能以一条光线来模拟
所以用几条光来模拟
您可找这方面的论文
关于GAUSSIAN BEAM DECOMPOSITION的
至于参数您参考说明书上吧

skai · 发表于 2003-5-28 01:08:00

您能帮我解释一下吗？

Photonics · 发表于 2003-5-28 19:52:00

ASAP模拟激光的方式
要先建立complex field distribution
再用DECOMPOSE把光束建立出来
它的参数M表示将GAUSSIAN BEAM切为几条BEAM
A则是定义BEAM的角度
试试下面的例子
这里有两条GAUSSIAN BEAM
一个不用DECOMPOSE

SYSTEM NEW
RESET

UNITS MM

PARABASAL 4
BEAMS COHERENT DIFFRACT
WIDTHS 1.6
WAVELENGTH 1.55 UM

GAUSSIAN Z 0 0 0 1 1 0 0 .001 .0003

WINDOW X Y
PIXELS 51
WINDOW X -2@3.5E-3 Y -2@3.5E-3
FIELD MODULUS 0
DISPLAY
PICTURE
RETURN

RAYS 0
DECOMPOSE DIR 0.1 45 !! Create new set of beams
FIELD MODULUS 0
DISPLAY
PICTURE
RETURN

skai · 发表于 2003-5-29 18:27:00

高斯光束的场分布不是有确定的形式吗？为什么还要定义角度？参数M为什么是小数？

Photonics · 发表于 2003-5-29 19:51:00

小数的意思是将总光束数乘上小数
就是说若总光束是10000而M=0.1这时
模拟的光线数就是1000
至于总光线数从何来,我就不清楚 ASAP常有这种问题
要问问原厂负责这领域的工程师
他们不同领域的工程师,也不一定清楚其它领域的ASAP功能
因为ASAP功能太多了
而高斯光束的部分,SORRY
也不清楚,我很少使用这功能

小马过河 · 发表于 2003-5-29 20:30:00

tracepro lighttool 可以完成高斯光束的模拟吗?

Photonics · 发表于 2003-5-29 23:42:00

可以

skai · 发表于 2003-6-2 17:30:00

好像不太行，因为是几何的方法。和用asap模拟的结果不同

Photonics · 发表于 2003-6-2 21:26:00

是的
他是模拟高斯能量分布

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