THORLABS SPDMA User manual

Single Photon Detector
SPDMA
Operation Manual
2021

Version:
Date: 1.0 08-Dec-2021
Copyright © 2021 Thorlabs

Foreword
Contents
1 General Information 1
11.1 Ordering Codes and Accessories
2 Getting Started 2
22.1 Parts List
3 Operating Instructions 3
33.1 Operating Elements 33.2 Mounting 33.3 Setup 43.4 Operating Principle 53.5 Block Diagram and Trigger IN
4 Maintenance and Service 7
74.1 Troubleshooting
5 Appendix 8
85.1 Technical Data 95.2 Definitions 105.3 Performance Plots 105.3.1 Typical Photon Detection Efficiency 105.3.2 Pulse Out Signal 115.4 Dimensions 125.5 Safety 145.6 Certifications and Compliances 155.7 Return of Devices 155.8 Manufacturer Address 155.9 Warranty 155.10Copyright and Exclusion of Liability 165.11Thorlabs Worldwide Contacts - WEEE Policy

© 2021 Thorlabs
We aim to develop and produce the best solutions for your
applications in the field of optical measurement techniques. To help
us to live up to your expectations and constantly improve our
products, we need your ideas and suggestions. We and our
international partners are looking forward to hearing from you.
Thorlabs GmbH
Warning
Sections marked by this symbol explain dangers that might result in
personal injury or death. Always read the associated information
carefully before performing the indicated procedure.
Please read this advice carefully!
This manual also contains "NOTES" and "HINTS" written in this form.
Attention
Paragraphs preceded by this symbol explain hazards that could
damage the instrument and the connected equipment or may cause
loss of data.
Note

Rev: 1.0, 08-Dec-2021 © 2021 Thorlabs Page 1
SPDMA 1 General Information
1 General Information
The Thorlabs' SPDMA Single Photon Detector uses a cooled silicon avalanche photodiode,
specialized for a wavelength range from 350 to 1100 nm with a maximum sensitivity at 600 nm.
Incoming photons are converted into a TTL pulse in the detector. The SMA connection offers a
direct output pulse signal from the module that can be viewed on an oscilloscope or connected
to an external counter.
An integrated Thermo Electric Cooler (TEC) element stabilizes the diode's temperature to re-
duce the dark count rate. The low dark count rate and high photon detection efficiency allow
detection of power levels down to fW. The active quenching circuit integrated into the diode of
the SPDMA enables high count rates. The output signal can further be optimized by continuous
adjustment using the Gain Adjustment Screw.
Using a TTL Trigger IN signal, the SPDMA can be externally triggered to select the time frame
for the detection of single photons.
Optical alignment is simplified by the relatively large active area of the diode with a diameter of
500 m m. The diode is actively aligned at the factory to be concentric with the input aperture,
which adds to the high quality of this device.
For flexible integration into optical systems, the SPDMA accommodates any Thorlabs 1'' lens
tubes as well as the Thorlabs 30 mm Cage System. The SPDMA can be mounted in metric or
imperial systems due to 8-32 and M4 combi-thread mounting holes.
The product includes an SM1T1 SM1 Coupler which adapts the external thread to an internal
thread and holds the SM1RR Retaining Ring and a reusable protective plastic cover cap.
Another advantage is that the SPDMA cannot be damaged by unwanted ambient light, which is
critical for many photomultiplier tubes.
Attention
Please find all safety information and warnings concerning this product in the chapter Safety in
the Appendix.
1.1 Ordering Codes and Accessories
SPDMA
Single Photon Detector, 350 nm - 1100 nm, Active Area Diameter 0.5 mm,
Combi-Thread Mounting Holes Compatible with 8-32 and M4 Threads
Included Accessories
· Power Supply (±12 V, 0.3 A / 5 V, 2.5 A)
· Plastic Cover Cap (Item # SM1EC2B) on an included SM1T1 SM1 Coupler with an
SM1RR SM1 Retaining Ring.
Optional Accessories
· All Thorlabs internal or external SM1 (1.035"-40) threaded accessories are compatible
with the SPDMA.
· The 30 mm Cage System can be mounted on the SPDMA.
Please visit our homepage http://www.thorlabs.com for various accessories like fiber adapters,
posts and post holders, data sheets and further information.

Page 2 MTN025859_D02
SPDMA 2 Getting Started
2 Getting Started
2.1 Parts List
Please inspect the shipping container for damage. Please do not cut through the cardboard, as
the box might be needed for storage or returns.
If the shipping container appears to be damaged, keep it until you have inspected the contents
for completeness and tested the SPDMA mechanically and electrically.
Verify that you have received the following items within the package:
1. SPDMA Single Photon Detector
2. Plastic Cover Cap (Item # SM1EC2B) on SM1T1-SM1 Coupler with an SM1RR-SM1
Retaining Ring
3. Power Supply (±12V, 0.3 A / 5 V, 2.5 A) with Power Cord, Connector According to Ordering
Country
4. Quick Reference

Rev: 1.0, 08-Dec-2021 © 2021 Thorlabs Page 3
SPDMA 3 Operating Instructions
3 Operating Instructions
3.1 Operating Elements
3.2 Mounting
Mounting SPDMA on an Optical Table
Mount the SPDMA on an optical post by using either of the three tapped mounting holes on the
left and right side, and bottom of the device. The combi-thread tapped holes accept both 8-32
and M4 threads, such that using either imperial or metric TR posts is possible.
Mounting External Optics
The customer system can be attached and aligned using either the external SM1 thread or the
4-40 mounting holes for a 30 mm Cage System. The positions are indicated in the Operating
Elements section. The external SM1 thread accommodates Thorlabs’ SM1-threaded (1.035"-
40) adapters that are compatible with any number of Thorlabs 1'' threaded accessories, like ex-
ternal optics, filters, apertures, fiber adapters, or lens tubes. The SPDMA is shipped with an
SM1T1 SM1 coupler that adapts the external thread to an SM1 internal thread. A retaining ring
in the coupler holds the protective cover cap. Please unscrew the coupler if needed.
For accessories, please visit our website or contact Thorlabs.
3.3 Setup
After mounting the SPDMA, set up the detector as follows:
1. Power up the SPDMA using the included power supply.
2. Switch on the SPDMA, using the toggle button on the side of the instrument.
3. Push the cover from the status LED to see the status:
a. Red: The LED will initially be red upon connection to the power supply to indicate this
connection and the need to wait until the detector has reached the operating temperature.
Within a few seconds, the diode is cooled down and the status LED will turn to green. The

Page 4 MTN025859_D02
SPDMA 3 Operating Instructions
status LED will return to red when the diode temperature is too high. If the LED is red, no
signal is sent to pulse output.
b. Green: Detector is ready for operation. The diode is at operating temperature and signal
arrives at the pulse output.
Note
The Status LED will turn red whenever the operating temperature is too high. Please ensure
sufficient air ventilation.
4. Push the cover back in front of the status LED to prevent LED light from disturbing the mea-
surement.
5. To increase the photon detection efficiency, turn the Gain Adjustment Screw with a slotted
screw driver (1.8 to 2.4 mm, 0.07" to 3/32"). For more information on the gain, please refer
to the chapter Operating Principle.
a. Use Minimum Gain when a low dark count rate is critical. This comes at the cost of low
photon detection efficiency.
b. Use Maximum Gain when it is desirable to collect a maximum number of photons. This
comes at the cost of a higher dark count rate.
c. Because the time between photon detection and signal output changes with the gain set-
ting, please reevaluate this parameter after changing the gain setting.
Note
"Trigger In" and "Pulse Out" are of a 50 W impedance. Make sure that the trigger pulse source
is capable to work on a 50 W load and that the device connected to "Pulse Out" operates at a
50 W input impedance.
3.4 Operating Principle
The Thorlabs SPDMA uses a silicon avalanche photo diode (Si APD), operated in reverse di-
rection and biased slightly beyond the breakdown threshold voltage VBR (see diagram below,
point A), also known as the avalanche voltage.
This operating mode is also known as "Geiger mode". An APD in Geiger mode will remain in a
metastable state until a photon arrives and generates free charge carriers in the PD's junction.
These free charge carriers trigger an avalanche (point B), leading to a significant current. An
active quenching circuit integrated into the APD limits the current through the APD in order to
avoid destruction and lowers the bias voltage below the breakdown voltage VBR (point C) im-
mediately after a photon released an avalanche. This enables high count rates with dead time
between counts down to the specified dead time at max gain. Afterwards the bias voltage is re-
stored.

Rev: 1.0, 08-Dec-2021 © 2021 Thorlabs Page 5
SPDMA 3 Operating Instructions
During the quenching time, which is known as the dead time of the diode, the APD is insensit-
ive to any other incoming photons.
Spontaneously triggered avalanches are possible while the diode is in a metastable state. If
these spontaneous avalanches occur randomly, they are called dark counts. An integrated
TEC element stabilizes the diode’s temperature below the ambient temperature to reduce the
dark count rate. This eliminates the need for a fan and avoids mechanical vibrations.
In case the spontaneously triggered avalanches are correlated in time with a pulse caused by a
photon, it is called an afterpulse.
Note
Due to APD properties, not all single photons may be detected. Reasons are the APD's intrinsic
dead time during quenching and the APD's nonlinearity.
Gain Adjustment
Using the gain adjustment screw, an overvoltage beyond the breakdown voltage can be adjus-
ted to the SPDMA. This increases the photon detection efficiency but also the dark count rate.
Please be aware that the probability of afterpulsing slightly rises with higher gain settings and
that adjusting the gain also affects the time between photon detection and signal output.
The dead time increases with decreasing gain.
3.5 Block Diagram and Trigger IN
The current pulse generated by an incoming photon passes a pulse shaping circuit, which is
shortening the APD's output TTL pulse duration. On the "Pulse Out" terminal the signal from
the pulse shaper is applied so that counts can be viewed on an oscilloscope or registered by an
external counter. In the absence of a Trigger, the gate is closed and allows signal out.
The Gain changes the Bias (overvoltage) on the APD. The Bias is physically guided through the
active quenching element but does not impact the active quenching.
TTL Trigger:
The TTL Trigger allows for selective activation of the pulse output: At high Trigger Input (spe-
cified in the Technical Data) the signal arrives at Pulse Out. This is the default whenever no ex-
ternal TTL signal is applied as a trigger.

Page 6 MTN025859_D02
SPDMA 3 Operating Instructions
Whenever a TTL trigger input signal is used, the default TTL input needs to be "Low". Signal
from photon detection is sent to Pulse Out as the Trigger Input voltage switches to "High". High
and Low signal are specified in the section Technical Data.
Note
"Trigger In" and "Pulse Out" are of a 50 W impedance. Make sure that the trigger pulse source
is capable to work on a 50 W load and that the device connected to "Pulse Out" operates at a
50 W input impedance.

Rev: 1.0, 08-Dec-2021 © 2021 Thorlabs Page 7
SPDMA 4 Maintenance and Service
4 Maintenance and Service
Protect the SPDMA from adverse weather conditions. The SPDMA is not water resistant.
Attention
To avoid damage to the instrument, do not expose it to spray, liquids or solvents!
The unit does not need regular maintenance by the user. It does not contain any modules
and/or components that could be repaired by the user. If a malfunction occurs, please contact
Thorlabs for return instructions.
Do not remove covers!
4.1 Troubleshooting
APD over temperature indicated
The temperature control circuit recognized that the actual temperature of the APD exceeded
the set point. Under normal operation conditions this should not happen, even after long term
operation. However, increase beyond the limits of the specified operating temperature range or
excessive thermal radiation on the detector can cause an overtemperature alert. The Status
LED will turn to red to indicate overheating.
Ø Ensure enough air flow around the device or provide external passive cooling.

Page 8 MTN025859_D02
SPDMA 5 Appendix
5 Appendix
5.1 Technical Data
All technical data are valid at 45 ± 15% rel. humidity (non condensing).
Item #
SPDMA
Detector
Detector Type
Si APD
Wavelength Range
350 nm - 1100 nm
Diameter of Active Detector Area
500 m m
Typical Photon Detection Efficiency (PDE)
at Gain Max
58% (@ 500 nm)
66% (@ 650 nm)
43% (@ 820 nm)
Gain Adjustment Factor (Typ)
4
Count Rate @ Gain Max.
Min
Typ
>10 MHz
20 MHz
Dark Count Rate
@ Gain Min
@ Gain Max
< 75 Hz (Typ); < 400 Hz (Max)
< 300 Hz (Typ); < 1500 Hz (Max)
Dead Time @ Maximum Gain
< 35 ns
Output Pulse Width @ 50 Ω load
10 ns (Min); 15 ns (Typ); 20 ns (Max)
Output Pulse Amplitude @ 50 Ω load
TTL High
TTL Low
3.5 V
0 V
Trigger Input TTL Signal 1
Low (closed)
High (open)
< 0.8 V
> 2 V
Afterpulsing Probability @ Gain Min.
1% (Typ)
General
Power Supply
±12 V, 0.3 A / 5 V, 2.5 A
Operating Temperature Range 2
0 to 35 °C
APD Operating Temperature
-20 °C
APD Temperature Stability
< 0.01 K
Storage Temperature Range
-40 °C to 70 °C
Dimensions (W x H x D)
72.0 mm x 51.3 mm x 27.4 mm (2.83 '' x 2.02 '' x 1.08 '')
Weight
150 g
1) Default in the absence of a TTL signal is > 2 V, allowing signal to the pulse output. The detector behavior is not
defined between 0.8 V and 2 V.
2) Non-condensing

Rev: 1.0, 08-Dec-2021 © 2021 Thorlabs Page 9
SPDMA 5 Appendix
5.2 Definitions
Active Quenching occurs when a fast discriminator senses the steep onset of the avalanche
current, released by a photon, and quickly reduces the bias voltage so that it is below break-
down momentarily. The bias is then returned to a value above the breakdown voltage in prepar-
ation for detection of the next photon.
Afterpulsing: During an avalanche, some charges can be trapped inside the high field region.
When these charges are released, they can trigger an avalanche. These spurious events are
called afterpulses. The life of those trapped charges is on the order of 0.1 µs to 1 µs. Hence, it
is likely that an afterpulse occurs directly after a signal pulse.
Dead Time is the time interval the detector spends in its recovery state. During this time, it is ef-
fectively blind to incoming photons.
Dark Count Rate: This is the average rate of registered counts in the absence of any incident
light and determines the minimum count rate at which the signal is dominantly caused by real
photons. The false detection events are mostly of thermal origin and can therefore be strongly
suppressed by using a cooled detector.
Geiger Mode: In this mode, the diode is operated slightly above the breakdown threshold
voltage. Hence, a single electron-hole pair (generated by absorption of a photon or by a
thermal fluctuation) can trigger a strong avalanche.
Gain Adjustment Factor: This is the factor by which the gain can be increased.
Saturation of the APD: The photon count by an APD is not exactly linearly proportional to the
incident optical CW power; the deviation increases smoothly with increasing optical power. This
non-linearity leads to the wrong photon count at high input power levels. At a certain input
power level, the photon count begins even to decrease with further increase in optical power.
Each delivered SPDMA is tested for appropriate Saturation behavior to resemble this example.

Page 10 MTN025859_D02
SPDMA 5 Appendix
5.3 Performance Plots
5.3.1 Typical Photon Detection Efficiency
5.3.2 Pulse Out Signal

Rev: 1.0, 08-Dec-2021 © 2021 Thorlabs Page 11
SPDMA 5 Appendix
5.4 Dimensions

Page 12 MTN025859_D02
SPDMA 5 Appendix
5.5 Safety
The safety of any system incorporating the equipment is the responsibility of the assembler of
the system.
All statements regarding safety of operation and technical data in this instruction manual will
only apply when the unit is operated correctly as it was designed.
The SPDMA must not be operated in explosion endangered environments!
Do not obstruct any air ventilation slots in the housing!
Do not remove covers or open the cabinet. There are no user-serviceable parts inside!
This precision device is only serviceable if returned and properly packed into the complete ori-
ginal packaging including the cardboard inserts. If necessary, ask for replacement packaging.
Refer servicing to qualified personnel!
Changes to this device cannot be made nor may components not supplied by Thorlabs be used
without written consent from Thorlabs.
Attention
Prior to applying power to the SPDMA, make sure that the protective conductor of the 3 con-
ductor mains power cord is correctly connected to the protective earth ground contact of the
socket outlet! Improper grounding can cause electric shock resulting in damage to your health
or even death!
All modules must only be operated with duly shielded connection cables.
Attention
The following statement applies to the products covered in this manual, unless otherwise spe-
cified herein. The statement for other products will appear in the respective accompanying doc-
umentation.
Note
This equipment has been tested and found to comply with the limits for a Class B digital
device, pursuant to Part 15 of the FCC Rules and meets all requirements of the Canadian
Interference-Causing Equipment Standard ICES-003 for digital apparatus. These limits are
designed to provide reasonable protection against harmful interference in a residential
installation. This equipment generates, uses, and can radiate radio frequency energy and, if not
installed and used in accordance with the instructions, may cause harmful interference to radio
communications. However, there is no guarantee that interference will not occur in a particular
installation. If this equipment does cause harmful interference to radio or television reception,
which can be determined by turning the equipment off and on, the user is encouraged to try to
correct the interference by one or more of the following measures:
· Reorient or relocate the receiving antenna.
· Increase the separation between the equipment and receiver.
· Connect the equipment into an outlet on a circuit different from that to which the receiver
is connected.
· Consult the dealer or an experienced radio/TV technician for help.
Users that change or modify the product described in this manual in a way not expressly ap-
proved by Thorlabs (party responsible for compliance) could void the user’s authority to operate
the equipment.

Rev: 1.0, 08-Dec-2021 © 2021 Thorlabs Page 13
SPDMA 5 Appendix
Thorlabs GmbH is not responsible for any radio television interference caused by modifications
of this equipment or the substitution or attachment of connecting cables and equipment other
than those specified by Thorlabs. The correction of interference caused by such unauthorized
modification, substitution or attachment will be the responsibility of the user.
The use of shielded I/O cables is required when connecting this equipment to any and all op-
tional peripheral or host devices. Failure to do so may violate FCC and ICES rules.
Attention
Mobile telephones, cellular phones or other radio transmitters are not to be used within the
range of three meters of this unit since the electromagnetic field intensity may then exceed the
maximum allowed disturbance values according to IEC 61326-1.
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).

Page 14 MTN025859_D02
SPDMA 5 Appendix
5.6 Certifications and Compliances

Rev: 1.0, 08-Dec-2021 © 2021 Thorlabs Page 15
SPDMA 5 Appendix
5.7 Return of Devices
This precision device is only serviceable if returned and properly packed into the complete ori-
ginal packaging including the complete shipment plus the cardboard insert that holds the en-
closed devices. If necessary, ask for replacement packaging. Refer servicing to qualified per-
sonnel.
5.8 Manufacturer Address
Manufacturer Address Europe
Thorlabs GmbH
Münchner Weg 1
D-85232 Bergkirchen
Germany
Tel: [phone]
Fax: [phone]
www.thorlabs.de
Email: [email protected]
EU-Importer Address
Thorlabs GmbH
Münchner Weg 1
D-85232 Bergkirchen
Germany
Tel: [phone]
Fax: [phone]
www.thorlabs.de
Email: [email protected]
5.9 Warranty
Thorlabs warrants material and production of the SPDMA for a period of 24 months starting
with the date of shipment in accordance with and subject to the terms and conditions set forth
in Thorlabs’ General Terms and Conditions of Sale which can be found at:
General Terms and Conditions:
https://www.thorlabs.com/Images/PDF/LG-PO-001_Thorlabs_terms_and_%20agreements.pdf
and
https://www.thorlabs.com/images/PDF/Terms%20and%20Conditions%20of%
20Sales_Thorlabs-GmbH_English.pdf
5.10 Copyright and Exclusion of Liability
Thorlabs has taken every possible care in preparing this document. We however assume no li-
ability for the content, completeness or quality of the information contained therein. The content
of this document is regularly updated and adapted to reflect the current status of the product.
All rights reserved. This document may not be reproduced, transmitted or translated to another
language, either as a whole or in parts, without the prior written permission of Thorlabs. Copy-
right © Thorlabs 2021. All rights reserved.
Please refer to the general terms and conditions linked under Warranty.

Page 16 MTN025859_D02
SPDMA 5 Appendix
5.11 Thorlabs Worldwide Contacts - WEEE Policy
For technical support or sales inquiries, please visit us at
https://www.thorlabs.com/locations.cfm for our most up-to-date contact information.
USA, Canada, and South America
Thorlabs, Inc.
[e-mail]
[e-mail]
UK and Ireland
Thorlabs Ltd.
[e-mail]
[e-mail]
Europe
Thorlabs GmbH
[e-mail]
Scandinavia
Thorlabs Sweden AB
[e-mail]
France
Thorlabs SAS
[e-mail]
Brazil
Thorlabs Vendas de Fotônicos Ltda.
[e-mail]
Japan
Thorlabs Japan, Inc.
[e-mail]
China
Thorlabs China
[e-mail]
Thorlabs 'End of Life' Policy (WEEE)
Thorlabs verifies our compliance with the WEEE (Waste Electrical and Electronic Equipment) direct-
ive of the European Community and the corresponding national laws. Accordingly, all end users in
the EC may return “end of life” Annex I category electrical and electronic equipment sold after
August 13, 2005 to Thorlabs, without incurring disposal charges. Eligible units are marked with the
crossed out “wheelie bin” logo (see right), were sold to and are currently owned by a company or in-
stitute within the EC, and are not dissembled or contaminated. Contact Thorlabs for more informa-
tion. Waste treatment is your own responsibility. “End of life” units must be returned to Thorlabs or
handed to a company specializing in waste recovery. Do not dispose of the unit in a litter bin or at a
public waste disposal site. It is the users responsibility to delete all private data stored on the device
prior to disposal.