以下我們使用一個(gè)很(hěn)簡單的共振器(qì)範例模型進行(xíng)功能示範

此範例将會(huì)示範如何使用GLAD。我們将使用resonator.inp這個(gè)檔案示範共振器(qì)。即使使用者對共振器(qì)不感興趣，這個(gè)範例也将會(huì)展示在GALD中解決問題的幾個(gè)重要步驟：
 初始化計(jì)算(suàn)機數(shù)組及單位
 選擇波長
 定義初始分布
 使用宏進行(xíng)重複運算(suàn)
 建立數(shù)據顯示計(jì)算(suàn)結果
此共振器(qì)将使用半對稱的結構進行(xíng)計(jì)算(suàn)，由半徑50cm的球面鏡及平面鏡所組成。共振器(qì)的長度為(wèi)46cm。輸出将由平面鏡輸出。下表1顯示其結構參數(shù)：

圖1-穩定的共振器(qì)結構。其光腰将會(huì)在平面鏡上(shàng)形成，及其相曲率将與曲面鏡的理(lǐ)想模态曲率相同

為(wèi)了簡化討(tǎo)論，我們将忽略增益及形成bare-cavity分析。我們開(kāi)始分析從準備一個(gè)命令檔案如下：

variab/dec/int pass
macro/def reson/o
pass = pass + 1 # increment pass counter
prop 45 # propagate 45 cm.
mirror/sph 1 -50 # mirror of 50 cm. radius
clap/c/n 1 .14 # .14 cm. radius aperture
prop 45 # propagate 45 cm. along beam
mirror/flat 1 # flat mirror
variab/set Energy 1 energy # set variable to energy value
Energy = Energy - 1 # calculate energy difference
udata/set pass pass Energy # store energy differences
energy/norm 1 1 # renormalize energy
plot/l 1 xrad=.15 # make a plot at each pass
macro/end
array/set 1 64 # set array size
wavelength/set 0 1.064 # set wavelengths
units/set 1 .005 # set .005 cm sample spacing
resonator/name reson # set name of resonator macro
resonator/eigen/test 1 # find resonator properties
resonator/eigen/set 1 # set surrogate beam to eigen mode
clear 1 0 # clear the array
noise 1 1 # start from noise
energy/norm 1 1 # normalize energy
pass = 0 # initialize pass counter
reson/run 100 # run resonator 100 times
title Energy loss per pass
plot/watch plot1.plt # set plot name
plot/udata min=-.05 max=.0 # plot summary of eigenvalues
title diffraction mode shape
set/density 32 # set plot grid to 32 x 32
set/window/abs -.05 .05 -.05 .05 # set plot window
plot/watch plot2.plt # set plot name
plot/iso 1 # make an isometric plot
以下就對每一項指令來(lái)做(zuò)介紹：
variab/dec/int pass
此行(xíng)定義一整數(shù)變量叫pass。我們将使用pass來(lái)儲存數(shù)據，變量如果不清楚的定義為(wèi)整數(shù)，将會(huì)被定義為(wèi)實數(shù)變量。

macro/def reson/o
此行(xíng)開(kāi)始定義宏，就像是子程序或函式一樣。所有(yǒu)介于macro/def與macro/end之間(jiān)的指令都将定義為(wèi)宏。這些(xiē)指令暫時(shí)不會(huì)被執行(xíng)。這些(xiē)指令列将被放在MACLIB中留待以後使用。這些(xiē)宏指令列将不需縮排。但(dàn)使用縮排将會(huì)使這些(xiē)指令更容易閱讀。