Working with the
application
Application pages
The application workspace is parted into pages, which are accessed via
the "Designer", "Beam", "Divergence" and "Modes loss" spines.
The laser cavity configuration is set on
the first page in the fields "L" (laser cavity
length), "RHR" (radius of
curvature of the high reflecting mirror), "ROUT" (radius of
curvature of the output mirror), "f" (focal length
of the lens), "ZL" (coordinate of
lens). On the same page, you need to set the wavelength in the "λ" field and the
lens diameter in the "DL"
field, which
will serve as a vertical scale and be used in calculating the modes
loss and beam divergence. It is assumed that the diameter of the lens
is the only limiter on the transverse size of the beam in the entire
laser cavity (this diameter is the aperture of the all system).
To set infinite values, type "inf".
To enter a number containing a decimal exponent, the character "E" is used. For example:
5.3х105
→ 5.3Е+5
0.7х10-7
→ 0.7Е-7
The values entered in the fields are accepted after
confirming the input with the "Enter"
key or when leaving the field (if the values are correct).
On the right side of the page the optical scheme of the
laser cavity is displayed. According
to the tradition accepted in the laser literature, the output of
radiation in the scheme is carried out to the right. The origin of the Z coordinate
axis is located at the location of the high reflecting
mirror. Mirrors and lens are considered thin.
View of the first page of the application.
Notations
on the optical scheme: DTEM00 is the TEM00
mode diameter, DFULL is the
diameter of the entire beam, ΘTEM00 is the TEM00
mode divergence, ΘFULL is the
divergence of the entire beam.
By pressings and by holdings the buttons with the "<<" and ">>" signs, you can vary the
parameter values up and down by the value specified in the "Step"
field. In this way, it is possible to select a laser cavity with the
desired beam caustic. The results of changing parameters are
immediately displayed on the scheme.
ADVICE. If it is not possible to find a lens with
which the laser cavity is stable, go to the third page and use the "Stability
Region" button to get a
hint.
The
application calculates two-mirror laser cavities with a lens inside.
They are equivalent to many real laser cavities, for which the internal
optics and thermo-optics can be represented by plane-parallel plates
and a thin lens. To take into account the plane-parallel plates
included in the laser cavity, it is necessary to set the equivalent
length as the length of the laser cavity, and the equivalent distance
from the high reflecting mirror to the lens as the coordinate of the
lens. The equivalent length and distance are calculated similarly to
finding the optical path along the optical axis from the high
reflecting mirror to the second mirror and from the high reflecting
mirror to the lens, with the only difference that instead of
multiplying by refractive indices, division is used. The Z
coordinate should be understood as the equivalent distance measured
from the high reflecting mirror. The lens diameter should be selected
as a beam size limiter. In typical cases, the lens is thermally induced
in the active element and can be assigned a diameter corresponding to
the generation region in the element. This assumes that the dimensions
of the mirrors and internal optical elements do not limit the beam more
than the lens aperture.
You can read about the calculation
algorithms in the "Calculation methods" section.
The
second page ("Beam")
displays a plot of the caustic calculated on the previous page for the
TEM00 mode and the entire beam. There you can also calculate
the field sizes and power focusing N in any section
inside the laser cavity by entering the coordinate in the "Z" field.
You
can read about the calculation algorithms in the "Calculation methods" section.
View of the second page of the application.
On the third page,
the dependence of the divergence in the selected range of the optical
power of the lens is calculated. The optical power range of the lens is
set by its boundaries in the "P1" and "P2" fields. You
can also calculate the divergence for a specific lens optical power
value by entering this value in the "P" field.
View of the third page of the application.
The "Stability region"
button serves to indicate the ranges of optical power of the lens in
which the laser cavity is stable.
The vertical lines on the plot mark the boundaries of stability.
You can read about the calculation algorithms in
the "Calculation methods" section.
On the
fourth page, plots of the dependence of the aperture loss of the
TEM00 - TEM22
Hermite-Gauss modes
on the optical power of the lens can be calculated. The optical
power range of the lens for the loss calculating is the same as
for calculating of the divergence. To change it, you need to return to
the "Divergence" page. The
modes for which you want to see a plot are selected from the list on
the left (marked with a tick by clicking the left mouse button).
The vertical lines on the
plot mark the boundaries of stability.

View of the fourth page of the application.
You can view the distribution of loss by TEM00 - TEM22 modes for a specific value of the optical power of the
lens after setting this value in the "P" field and
clicking the "Loss distribution"
button. After clicking the button, the following window will be
displayed:

View of the loss
distribution window.
To return back, close this
window with the "Close" button
(or select the "Quit" item from
the "File" menu of the window).
You can read about the
calculation algorithms in the "Calculation methods" section.
When
you exit the application, the geometric settings of the application are
saved (i.e., the application font size, the application position
on the screen,
the application window size), as well as the settings for the accuracy
of viewing results and for exporting plots points to text, optical
scheme parameters, and paths to recent files. They are loaded the next
time you start the application and you can continue to work on their
base. Moreover, sessions and settings files can be used, as described
below.
Features that available through the
application menu
Working with
sessions. The
session contains all the application settings, except for geometric
ones (i.e., the application font size, the application position on the
screen, the application window size); includes settings for the laser
cavity parameters, settings for the accuracy of viewing results and for
exporting plots points to text, paths to the latest files. Sessions can
be saved and loaded. You can start the default session with the initial
settings. Working with sessions is carried out using the "File/Sessions"
menu.
Features that
available through the "Settings" item. Using the sub-items of
this menu item, it's possible to change the font
size of the application, the accuracy of viewing of the results, the
settings for exporting plots points to text; also, it's possible to
save to a
file, read from a file and reset to the default state all these
settings.
Saving pictures. You can save
pictures displayed on the pages of the application (scheme, plots) to
files in vector (pdf and svg files) and raster (png and jpeg files) format using the
sub-items of the application "File/Save picture" menu,
selecting a folder, file extension and entering the file name in the
dialog box that opens. The picture that is on the current page is
saved. Also, pictures can be copied to the clipboard in raster format by
means of the menu called by the mouse right
button clicking in the picture area. For plots, it is
possible to save points in the form of a table of values to a text
file by means of the main menu and to the clipboard - using the menu
called by the mouse right button clicking
in the plot area. The "Loss
distribution"
window has similar possibilities, except for working with a table of
values (the values are displayed in the window itself on the right).
Printing pictures. The picture
(scheme or plot) displayed on the current page of the application can
be printed. The menu item "File/Print..."
is used for this aim. Selecting this item opens a dialog box with a
preview and print settings. If
necessary, do print preferences
using this dialog box
and click the printer icon at the top right. Similar functionality is
implemented for the "Loss distribution"
window.
Brief report generation. Using
the application "File/Brief report..." menu item, it's possible to create a report that
includes the laser
cavity optical scheme, its
parameters and the results of calculating for the beam as a whole and
for the TEM00
mode (size of field in each optical element, divergence). You can
add your comment to the report. The report is saved as a pdf file. If desired, it can be send
to a printer from third-party applications for working with pdf files (Adobe Reader, Foxit Reader, etc.).