THORLABS Redstone OSA305 User manual

RedstoneTM OSA305,
Optical Spectrum
Analyzer
Quick Start Guide

Redstone™ OSA305
Table of Contents
Chapter 1 Warning Symbol Definitions ...........................................1
Chapter 2 Safety.................................................................................2
Chapter 3 Using the OSA ..................................................................3
3.1. Introduction................................................................... 3
3.1.1. Software.......................................................................................3
3.2. Setup and Installation.................................................... 3
3.2.1. Starting the Application................................................................4
3.2.2. Overview: Software Interface ......................................................5
3.3. Optical Alignment.......................................................... 5
3.3.1. Optical Setup...............................................................................6
3.3.2. Initial Visual Alignment ................................................................6
3.3.3. Final Alignment using the OSA....................................................6
3.3.4. Example setups...........................................................................8
3.4. Starting a Measurement ................................................ 9
3.4.1. Sensitivity and Resolution ...........................................................9
3.4.2. Saving Your Data ......................................................................10
3.5. Functions and Appearance........................................... 10
3.5.1. Interferogram View vs Spectrum View ......................................10
3.5.2. Using Markers............................................................................10
3.5.3. Analysis Tools ...........................................................................11
3.5.4. Display appearance...................................................................11
Chapter 4 Regulatory.......................................................................12
Chapter 5 Thorlabs Worldwide Contacts.......................................13

Redstone™ OSA305 Chapter 1: Warning Symbol Definitions
Rev B, December 15, 2021 Page 1
Chapter 1 Warning Symbol Definitions
Below is a list of warning symbols you may encounter in this manual or on your
device.
Symbol
Description
Direct Current
Alternating Current
Both Direct and Alternating Current
Earth Ground Terminal
Protective Conductor Terminal
Frame or Chassis Terminal
Equipotentiality
On (Supply)
Off (Supply)
In Position of a Bi-Stable Push Control
Out Position of a Bi-Stable Push Control
Caution: Risk of Electric Shock
Caution: Hot Surface
Caution: Risk of Danger
Warning: Laser Radiation
Caution: ESD Sensitive Components

Redstone™ OSA305 Chapter 2: Safety
Page 2 STN053070-D03
Chapter 2 Safety
All statements regarding safety of operation and technical data in this instruction
manual will only apply when the unit is operated correctly.
SHOCK WARNING
High voltage inside. To avoid electrical shock, prior to powering on the unit,
make sure that the protective conductor of the 3-conductor power cord is
correctly connected to the protective earth contact of the socket outlet.
Improper grounding can cause electric shock, resulting in severe injury or even
death. Do not operate without the cover installed.
CAUTION
This unit must not be operated in explosive environments. If purging gas other
than dry air is used, make sure that the environment for the operator is well
ventilated since the gas will leak out from the instrument. This product is for
indoor use only. To prevent potential fire or shock hazard, do not expose the
unit to any source of excessive moisture. Only use the instrument standing on
its feet.
WARNING
The Redstone OSA305 includes a red laser and an infrared laser. The
classification of these lasers follows the European Standard IEC 60825-1:2014.
Viewing the laser output with telescopic optical instruments (for example,
telescopes and binoculars) close to the aperture may pose an eye hazard! Using
the instrument in combination with collimating optics may have an impact on
the assigned laser classification. The safety of any system incorporating the
equipment is the responsibility of the assembler of the system.
Use of controls or adjustments or performance of procedures other than those
specified herein may result in hazardous radiation exposure.

Redstone™ OSA305 Chapter 3: Using the OSA
Rev B, December 15, 2021 Page 3
Chapter 3 Using the OSA
3.1. Introduction
The Redstone Optical Spectrum Analyzer (OSA) is a general-purpose spectrum
analyzer for optical research and production applications. It has a user-friendly
Graphical User Interface (GUI) and can be controlled from a Windows®10 PC via
a High-Speed USB 3.0 port. It is equipped with an FC/PC fiber input receptacle
and a free-space input window for collimated beams up to Ø10 mm; however,
special designs with other input receptacles are available on request. The
frequency-locked reference laser can be accessed via the FC/APC connector on
the front panel. The instrument is designed for measurements of continuous-wave
(CW) light sources but works in some applications where pulsed light is used.
Please contact Technical Support at [e-mail] to discuss your
application if you have a pulsed source.
Figure 1 Front View of the Redstone OSA305
3.1.1. Software
The Redstone OSA305 is shipped with the software package pre-installed on the
laptop computer that is included with the purchase of this instrument. The software
has a customizable GUI for acquiring, inspecting, manipulating, and analyzing
spectra and interferograms. The software makes it easy to locate and track
spectral peaks or valleys, measure the optical input power over any wavelength
range, calculate an absorption spectrum in real-time, or track a large number of
parameters over time.
For usage with other computers the software is downloadable from the webpage.
3.2. Setup and Installation
Place the OSA on a flat and stable surface, and if the free-space input is to be
used, it is recommended to use two Thorlabs CF175 clamping forks on the
Fiber Port
Free-Space Port
Calibration Output

Redstone™ OSA305 Chapter 3: Using the OSA
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mounting feet to secure the OSA to an optical table, as shown in Figure 2. This will
lock the interferometer to the optical table and reduce any vibrations that might
interfere with the measurements.
Figure 2 Using two CF175 clamping forks (marked with arrows), the Interferometer
Assembly can be Locked to the Table
Once the OSA is placed correctly on the table, attach the power cable and connect
the OSA to the computer with the OSA software installed (make sure that the
software is installed on the computer before connecting the OSA), using an
available USB 3.0 port on the PC and the included USB cable. After connecting
the instrument to the PC, the operating system will load the appropriate USB
drivers for the OSA. Please wait for this procedure to finish before doing anything
else.
3.2.1. Starting the Application
Start the application “Thorlabs Redstone OSA.”When the Thorlabs OSA
application starts, it will automatically detect all Thorlabs Redstone Optical
Spectrum Analyzers connected to the PC. A list of all connected OSAs can be
seen by clicking the button “Devices” found under the Instrument menu.

Redstone™ OSA305 Chapter 3: Using the OSA
Rev B, December 15, 2021 Page 5
3.2.2. Overview: Software Interface
Figure 3 The main software interface with different menu selections marked with
arrows, as well as the Status bar and Data display window
The Main menu (see Figure 3) contains all the common commands, from starting
a measurement to analysis of the spectrum and mathematical operations. The
Settings bar is located below the Main menu, providing easy access to common
instrument settings and settings for the axes, 2nd x-axis etc. By clicking a Trace
label, the Trace drop down menu is shown, where one can select input source,
load a spectrum, clear the data, display trace data, and more. The bulk of the
window is made up of the Data display area, where the spectra are plotted. The
Status bar, indicating if the instrument is performing a measurement and
information about the last successful measurement, is shown at the very bottom.
3.3. Optical Alignment
When using the fiber input port, no further alignment is necessary; an internal
reflective collimator will collimate the beam and redirect it into the interferometer.
However, when using the free-space port, it is important to ensure good alignment.
This document will give some general tips; for more details, please see the “Free-
space Alignment Tutorial”, which can be opened by clicking the “Help” button in
the Help menu.
Please ensure that the optical power of the input light does not exceed the
maximum allowed power of 10 mW.
Trace Controls
Main Menu
Settings Bar
Status Bar
Data Display

Redstone™ OSA305 Chapter 3: Using the OSA
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3.3.1. Optical Setup
To simplify the alignment, two mirrors in kinematic mounts should be used between
the test source and the OSA, where one mirror is close to the source and the other
is close to the OSA free-space port. Please see Figure 4 and Figure 5 for
suggestions of mirror placement. If the beam height of your experimental setup is
not consistent with the free-space input, the two mirrors and the distance between
them make it possible to adjust the beam height to that of the OSA’s input. Note
that there is no need to keep the optical path parallel to the optical table until after
the mirror closest to the OSA.
3.3.2. Initial Visual Alignment
Use the mirror closest to the test source to center the input beam on the OSA input.
A viewing card, such as Thorlabs Item #s VRC2 or VRC6S, and/or an alignment
plate, such as Thorlabs Item # CPA2, can be used to aid in the alignment. Then,
open the “Free-space Alignment” window from the Instrument menu, activate the
alignment beam, and use the mirror closest to the OSAto point the alignment beam
at the center of the input source. Repeat adjusting the two mirrors in turn until both
conditions are fulfilled; the two beams then overlap over the entire beam path. To
further optimize the alignment, the DC signal value of the detectors are shown
whenever the alignment beam is active. Maximizing these values will most often
lead to good interferometric signal values.
3.3.3. Final Alignment using the OSA
Once the system is roughly aligned, deactivate the alignment beam in order to see
a spectrum in the main software window. Change the settings to Low Resolution
and Low Sensitivity and start a continuous measurement. Use the “Free-Space
Alignment” window to adjust the gain levels. First, adjust the gain levels until the
signal values lie between about 10% to 80%. Note that if the source is weak, the
sensitivity may need to be increased, as this enables higher gain levels for some
detectors. However, this will also slow down the measurements. If the source is
strong, the attenuation filters can be activated through the “Free-Space Alignment”
window.
To optimize the alignment, there are several software analysis tools that can be
used. In addition to the signal values in the “Free-Space Alignment” window, it is
recommended to survey the detected optical power by using the Power tool (under
the Analysis menu) and to observe either the interferogram or spectrum. A time
series measurement of the signal and/or power can be started via the “Long-Term”
functionality (see Section “Long-Term Analysis” in the manual) to get a reading of
how these values change as you adjust the two mirrors.
Once the desired software tools are selected, repeat the alignment procedure
described above but utilize the OSA readings instead of the viewing card to
optimize the alignment. Remember to decrease the gain level and/or activate the
attenuation filter if any detector gets close to saturation.

Redstone™ OSA305 Chapter 3: Using the OSA
Rev B, December 15, 2021 Page 7
When the “Free-space Alignment” window is closed, and whenever necessary
during normal operation such as when the input source conditions have changed
considerably, the autogain algorithm will run a series of short sweeps to determine
optimal gain and offset settings. An overlay window will appear during this time
advising the user to wait for optimization to complete.

Redstone™ OSA305 Chapter 3: Using the OSA
Page 8 STN053070-D03
3.3.4. Example setups
Figure 4 and Figure 5 display two common scenarios involving the free-space input
port.
Figure 4 Free-Space setup suitable for a Collimated Source, using a Laser Diode
mounted in a Thorlabs LDM56 Laser Diode Mount. Two mirrors are used to
facilitate the Alignment Process and to adjust beam height.
Figure 5 Free-Space setup suitable for a Broadband Divergent Source, in this case
illustrated with Thorlabs SLS203L Stabilized Light Source. The source is kept at
a short distance from the OSA to minimize input losses.