THORLABS Chromatis User manual

Chromatis™
Dispersion Measurement System
User Guide

Chromatis™ Dispersion Measurement System
Table of Contents
Chapter 1 Safety.........................................................................................................................1
Chapter 2 Description.................................................................................................................3
Chapter 3 Instrument Overview..................................................................................................5
Chapter 4 Measurement.............................................................................................................8
4.1.1 Zero-Degree Reflection and Transmission Fixture (Ø1” and Ø1/2” Optics) ........................................................ 9
4.1.2 Angle of Incidence Reflection Fixture................................................................................................................ 10
4.3.1 Configuration Settings Tab................................................................................................................................ 18
4.3.2 Motor Control Tab............................................................................................................................................. 20
4.3.3 S-Polarization Tab.............................................................................................................................................. 20
4.3.4 P-Polarization Tab ............................................................................................................................................. 21
Chapter 5 Reference Optics and Calibration ..............................................................................22
Chapter 6 Wavelength Selection Filters and Detector Gain Settings...........................................23
Chapter 7 Changing Detectors...................................................................................................25
Chapter 8 Specifications ...........................................................................................................27
Chapter 9 Mechanical Drawings................................................................................................ 28
Chapter 10 Certifications and Compliance...................................................................................30
Chapter 11 Warranty and RMA Information................................................................................31
Chapter 12 Thorlabs Worldwide Contacts ...................................................................................32

Chromatis™ Dispersion Measurement System Chapter 1: Safety
Rev. A, September 27, 2022 Page 1
Chapter 1 Safety
Warning
All statements regarding safety of operation and technical data in the manual will only apply
when the unit is operated correctly as it was designed for.
Laser Radiation Warning
The user may be exposed to laser signals after they have been attenuated via internal
components to < 1 mW in the range of 500 - 650 nm, which is Class II laser radiation. Use of
controls or adjustments or performance of procedures other than those specified herein may
result in hazardous radiation exposure.
Do not look into the optical output when the device is operating. Always disable the light
sources with the instrument head on-off switch before changing detectors, optics, or
measurement fixtures. It is possible that a Class 1 laser product with a highly diverging beam
can produce high enough irradiance levels near to or in contact with the source (for instance,
a fiber tip) so that skin or iris injury is possible.
Shock Warning
Before poweringthe unit on, make sure that the line voltage range marked on the power supply
agrees with your local supply, and 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 cover
installed.
Remove the AC power cord before changing the light bulb in the power supply. Do not open
the power supply when the device is connected to power. The power supply contains AC power
and will put the user at risk of shock.
Explosion Warning
This instrument must not be operated in an explosion endangered environment.

Chromatis™Dispersion Measurement System Chapter 1: Safety
Page 2 TTN202268-D02
Warranty
Do not open the CHROMATIS Dispersion Measurement System housing. There are no user-
serviceable parts in this product. Opening the device will void your warranty. Any modification
or servicing of this system by unqualified personnel renders Thorlabs free of any liability. This
device can only be returned when packaged into the complete original packaging, including all
foam packing inserts. If necessary, ask for replacement packaging.
Note: This equipment has been tested and found to comply with the limits for a Class A digital device, pursuant
to part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful
interference when the equipment is operated in a commercial environment. This equipment generates, uses, and
can radiate radio frequency energy and, if not installed and used in accordance with the instruction manual, may
cause harmful interference to radio communications. Operation of this equipment in a residential area is likely to
cause harmful interference in which case the user will be required to correct the interference at his own expense.
This device must only be operated with proper shielded connection cables. This product has been tested and
found to comply with the limits according to IEC 61326-1 for using connection cables shorter than 3 meters
(9.8 feet).
Laser Safety Precautions
It is recommended that all persons who use or are near devices emitting laser light be aware of the potential
hazards.
•Never look into the end of an optical cable connected to an optical output device that is operating. Direct
exposure to laser radiation can severely injure the human eye.
•Eye and skin exposure to direct or scattered laser radiation is hazardous and is considered potentially
extremely harmful.
•Install the laser in an enclosed area with access restricted to trained personnel. Clearly label the area and
mark the entrance with the class of laser (Class II).
•Never leave the optical outputs of the device on and unattended.
•Ensure that this device is not assembled, operated, or repaired by inexperienced or untrained personnel.
•Ensure that all mirrors and optics used are securely positioned and fixed to prevent movement. Prevent
stray reflections from surfaces at all times.
•Do not allow reflective objects to be placed in the laser beam outputs of this device. Laser light scattered
from a reflective surface can be as damaging as the original beam. Objects such as rings, watchbands, and
metal pens or pencils can be hazardous.
•Install the device so that the laser beam outputs are not at eye level.

Chromatis™ Dispersion Measurement System Chapter 2: Description
Rev. A, September 27, 2022 Page 3
Chapter 2 Description
The Chromatis is a white light interferometer (WLI) designed to measure the dispersion characteristics of reflective
and transmissive optics. The WLI itself can be implemented as a simple interferometer as shown in Figure 1.
Figure 1 White Light Interferometer: A broadband, temporally incoherent light source (such as a
halogen bulb) is collimated and sent through an interferometer consisting of a broadband, low
dispersion beamsplitter, and two delay arms. One arm (reference arm) uses a low dispersion mirror,
while the other arm (test arm) contains the test mirror. The time delay (Δt) between the two arms is
scanned across Δt = 0. In the regions around Δt = 0, the white light signals from each arm interfere
with each other, giving an interference pattern that is detected by a photodiode and recorded by a
computer. To provide a distance reference for the time delay scan, a coherent source (HeNe laser) is
co-propagated with a vertical offset to the white light. The HeNe fringes are recorded on a separate
photodiode.
The white light interference pattern contains information about the relative phases of the light from the test arm
and the reference arm. A computer is used to process the interference pattern and extract the phase and
dispersion properties of the mirror under test. This device also can measure the dispersion of a transmissive
sample by replacing the test mirror with a low dispersion mirror and placing the transmissive sample in the beam
path.
The Chromatis dispersion measurement system directly measures the phase of the optic under test and converts
the phase to dispersion through numerical derivatives
a
:
𝑃ℎ𝑎𝑠𝑒 = 𝜑
𝐺𝑟𝑜𝑢𝑝 𝐷𝑒𝑙𝑎𝑦 (𝐺𝐷) = 𝑑𝜑
𝑑𝜔
a
More in-depth information can be found in: S. Diddams and J. Diels, "Dispersion measurements with white-light
interferometry," J. Opt. Soc. Am. B 13, 1120-1129 (1996).

Chromatis™Dispersion Measurement System Chapter 2: Description
Page 4 TTN202268-D02
𝐺𝑟𝑜𝑢𝑝 𝐷𝑒𝑙𝑎𝑦 𝐷𝑖𝑠𝑝𝑒𝑟𝑠𝑖𝑜𝑛 (𝐺𝐷𝐷) = 𝑑2𝜑
𝑑𝜔2
𝑇ℎ𝑖𝑟𝑑 𝑂𝑟𝑑𝑒𝑟 𝐷𝑖𝑠𝑝𝑒𝑟𝑠𝑖𝑜𝑛 (𝑇𝑂𝐷) = 𝑑3𝜑
𝑑𝜔3
𝐹𝑜𝑢𝑟𝑡ℎ 𝑂𝑟𝑑𝑒𝑟 𝐷𝑖𝑠𝑝𝑒𝑟𝑠𝑖𝑜𝑛 (𝐹𝑂𝐷) = 𝑑4𝜑
𝑑𝜔4
This method of dispersion measurement is very versatile because only a single element detector is needed for the
white light measurement and automatic wavelength calibration is built-in because of the HeNe optical reference.
This means that a dispersion measurement can be made at any wavelength that you can provide a broad
bandwidth source and a detector. In addition, an increase in real resolution is obtained by scanning over a longer
delay.
There are some practical limitations to this measurement. The Chromatis dispersion measurement system uses a
fiber-coupled white light source, which simplifies the optical setup but introduces some wavelength limitations.
Typical fiber optic cables attenuate more in the visible and greatly in the UV. In addition, the white light source
was chosen to provide the broadest measurement bandwidth possible and to provide a smooth spectral curve.
The white light source in the Chromatis allows easy characterization of mirrors designed for Ti:sapphire (around
800 nm), Yb:fiber (around 1030 nm), and Er:fiber (around 1550 nm) lasers, along with some harmonics. The output
spectrum from the white light source tapers off greatly in the visible and has no light output below 360 nm. The
typical configuration of the Chromatis system includes a silicon detector, which can measure from 500 nm to 1100
nm. For NIR applications, a InGaAs detector operating over the 900 nm to 1650 nm wavelength is also available
separately.
In addition, real world measurement issues like light noise, amplifier noise, and digitization put a limit on the
amount of time delay you can scan before the integrated noise becomes greater than the signal. Chromatis uses
low noise components, but the time delay scan still is limited to less than approximately 10,000 fs for typical
measurements. At this level, absolute noise is high, but very sharp and very high dispersion features can be
resolved; however, most optics do not require this extreme resolution. Optics that do require this resolution have
very large dispersions and the relative noise is still very low (GDD noise/GDD value). At more moderate resolutions
(5 nm is ideal for most optics), both the absolute and relative noise is low and standard deviations of less than 5
fs2are typical over most of the measurement range for only a few scans. The Chromatis software interface has
built-in averaging so that the effects of this noise can be reduced simply by increasing the number of scans.

Chromatis™ Dispersion Measurement System Chapter 3: Instrument Overview
Rev. A, September 27, 2022 Page 5
Chapter 3 Instrument Overview
Optical Head and Fixtures
The Chromatis instrument is designed to be easy to use. There are two separate user-swappable fixtures available
that enable three different measurement types for Ø1/2” and Ø1” optics, which are discussed in the next chapter.
For fixtures that enable measurements on a mirror-pair or Ø2” optics, please contact [e-mail].
Figure 2, Figure 3, and Figure 4 show an overview of the Chromatis optical head.
Figure 2 The Chromatis Optical Head: The fixture being used for the current measurement is
installed in the measurement area. The fixture not in use can be locked to the baseplate in the
fixture storage area. The detectors are contained in a user-accessible section; the included silicon
detectors can be replaced with the CHRDETN InGaAs detectors for NIR applications. The light
selection switch and emission indicator are shown on the front of the device. The umbilical and
data port is on the side.
Umbilical
and Data
Port
Light
Selection
Switch
Fixture
Installed for
Measurement
Fixture Storage
Area
Detectors
Alignment Knob
Alignment Viewing Screen

Chromatis™Dispersion Measurement System Chapter 3: Instrument Overview
Page 6 TTN202268-D02
Figure 3 The custom optic holders have thumbscrews for easy optic mounting while standard
mirror mounts use a typical setscrew mounting. The thumbscrews on the custom optic holders
contain spring-loaded nylon tips to provide the right amount of mounting force on the optics.
Figure 4 Umbilical and Data Port: This panel contains the instrument ON/STANDBY switch. The on
position is denoted by “I” and the standby position is denoted by “O”. The silver cable is the fiber
optic cable carrying the light from the various light sources to the instrument head. The D-sub
connector provides power and control for the various components of the Chromatis system. The
USB Motor and Data connections are plugged directly into the included laptop computer.
Power Supply Unit
The electronics for Chromatis dispersion measurement system are contained within a rack-mountable 2U
enclosure, which also can operate free-standing. There only is one user-serviceable component within the power
supply enclosure: the white light source bulb. Instructions on how to replace the white light bulb are included
with each device. There is a power switch in the back of the power supply enclosure (Figure 5) that should remain
on unless the instrument is being moved or the bulb is being replaced. When the Chromatis system is not in use,
or when optics, measurement fixtures, or the photodiodes are being removed, turn the instrument off using the
on-standby switch on the optical head (shown in Figure 4), but leave the power supply on-off switch in the On
position. This will disable all the laser light sources for increased safety and longevity. Leaving the power supply
on ensures that the motor position does not have to be re-established each time the instrument is used.
Polaris
Mount
Setscrew
Thumbscrew
On/Standby
Switch
USB 2.0 Type-B
Connector
USB 2.0 Type-B
Connector
15-Pin Male
D-Sub Connector
Fiber Optic Cable
for Light Sources
(Not Removable)

Chromatis™ Dispersion Measurement System Chapter 3: Instrument Overview
Rev. A, September 27, 2022 Page 7
Figure 5 Chromatis power supply front (upper picture) and back (lower picture) panels. The power
supply on-off switch is next to the power cord plug. The umbilical cables plug into the Fiber Out
and Power Out ports.
Shipping List
The Chromatis dispersion measurement system contains the following components:
•Chromatis Optical Head (Armored Fiber Cable is Permanently Attached)
•Dust Cover for Optical Head
•Chromatis Power Supply Unit
•0° Reflection and Transmission Precision Fixture
•Angle of Incidence Reflection Precision Fixture
b
•Calibrated System Optic for Transmission Measurements
•Calibrated Reference Optics (Qty. 2)
•AD1 Ø1" OD Adapter for Ø1/2" Optic, 0.25" Thick
•Laptop with Pre-Installed Software
•USB 2.0 Type-A to Type-B Cable, 10' (3.05 m) Length (Qty. 2)
•15-Pin D-Sub Cable, Female to Male, 10' (3.05 m) Length
•Region-Specific AC Power Cord
•Torx T10 Key for White Light Bulb Replacement
b
The sliding portion of the angle of incidence reflection fixture, which includes a POLARIS-K1 mirror mount with the mounted
calibrated system optic, is packaged separately from the fixture.
15-Pin Female D-Sub
Connector
AC Power
Input
Light Source
Output Port
(SMA Connector)
On/Off
Power Switch

Chromatis™Dispersion Measurement System Chapter 4: Measurement
Page 8 TTN202268-D02
Chapter 4 Measurement
Alignment and Fixture Overview
The Chromatis dispersion measurement system is designed to enable easy and fast measurements of mirrors and
transmissive optics in three different modes of operation: zero-degree reflection, transmission, and angled
reflection. The included fixtures are mechanically registered and easily swappable. There are two separate fixtures
that provide these different measurements, as described below. For a fixture that facilitates measurements on a
complimentary mirror pair, please reach out to [e-mail].
Figure 6 The Chromatis optical head showing the fixture measurement position. Fixtures are
interchangeable and allow different measurement modes.
Figure 7 Fixture locking and unlocking occurs through rotation of the locking wheel in the fixture
baseplate. Rotate the wheel to the left to lock a fixture into place and rotate the wheel to the right
to unlock a fixture for removal from the baseplate.
Please note that no tools are necessary to change fixtures. Do not remove the fixture baseplate or loosen any of
the screws affixing the baseplate to the instrument breadboard.
Fixture
Location