THORLABS DET10A Operating Manual

PO Box 366, 435 Route 206N, Newton, NJ 07860

2

-

14

Ph [phone], Fax [phone], http://www.thorlabs.com

DET10A Operating Manual – High Speed GaP Detector

Description:

The Thorlabs DET10A is a ready-to-use high-speed photo detector. The unit comes complete with a photodiode and
internal 12V bias battery enclosed in rugged aluminium housing. The DET10A includes a removable 1” optical
coupler (SM1T1), providing easy mounting of ND filters, spectral filters, fiber adapters (SMA, FC and ST style), and
other Thorlabs 1” stackable lens mount accessories.

The DET10A includes two #8-32 tapped mounting holes with a 0.25” mounting depth, while the DET10A/M has two
M4 tapped mounting holes. A 12V A23 battery is included.

Specifications:

Electrical

Detector: Silicon PIN

Active Area: 0.8mm

Wavelength Range:

Peak Wavelength:

Peak Response (typ):

Diode Capacitance: CJ 6pF

Rise/Fall Time: tr / tf 1ns (max.)

Linearity Limit (Current): 1mA

(Power):

NEP (750nm):

Bias Voltage: V

Dark Current2: ID 0.3nA (2nA max.)

Output Voltage: V

1. All measurements performed with a 50Ω load unless stated otherwise.

2. Measured with specified Bias Voltage.

3. Assumes the battery voltage drops below 9.6V. The reverse protection diode generates a 0.6V drop.

λ

λp

ℜ(λp)

10V (9V min)

BIAS

0 to 10V

OUT

(Ø1.0 mm)
200 to 1100 nm
750 nm (typ)

0.45 A/W (typ)

2mW (min @ λP)

1.9x10

W/√Hz (max.)

Figure 1 – DET10A Spectral Responsivity Curve

General

70mm x 48mm x 21mm

On / Off Switch: Slide

Output: BNC (DC Coupled)

Package Size: 2.8”x1.9” x 0.83”

PD Surface Depth: 0.12” (3.1mm)

Weight: 0.2 lbs

Accessories: SM1T1 Coupler

SM1RR Retainer Ring

Storage Temp:

Operating Temp:

Battery: A23, 12VDC, 40mAh

Low Battery Voltage3 (See ‘Battery Check’)

V

(Hi-Z): ~9V

OUT

V

(50Ω):

OUT

-25 to 70°C
10 to 50°C

~400mV

13052-S01 Rev C 11/8/2011

Page 1 of 5

Operation

Thorlabs DET series are ideal for measuring both pulsed and CW light sources. The DET10A includes a reverse­biased PIN photo diode, bias battery, and ON/OFF switch packaged in a rugged housing. The BNC output signal is
the direct photocurrent out of the photo diode anode and is a function of the incident light power (P) and wavelength
(λ). The Spectral Responsivity, ℜ(λ), can be obtained from Figure 1 to estimate the amount of photocurrent to
expect. Most users will wish to convert this photocurrent to a voltage (V
This is accomplished by adding an external load resistance, R

V

= P * ℜ(λ) * R

OUT

. The output voltage is derived as:

LOAD

LOAD

It should be noted that the load resistor will react with the photodetector junction capacitance (CJ) to limit the
bandwidth. For best frequency response, a 50Ω terminator should be used. The bandwidth (fBW) and the rise-time
response (tR) can be approximated using the diode capacitance (CJ) and the load resistance (R

fBW = 1 / (2 * π * R

tR = 0.35 / f

LOAD

BW

* CJ)

For maximum bandwidth, we recommend using a 50Ω coax cable with a 50Ω terminating resistor at the opposite end
of the coax. This will also minimize ringing by matching the coax with its characteristic impedance. If bandwidth is not
important, you may increase the amount of voltage for a given input light by increasing the R

) for viewing on an oscilloscope or DVM.

OUT

) as shown below:

LOAD

.

LOAD

ON/OFF

SWITCH

BATTERY

PROTECTION

+

DIODE

R

VBAT

VOLTAGE

REGULATOR

5V

Figure 2 – Circuit Schematic

1K

VBIAS
NOISE
FILTER

VBIAS

PHOTO

DETECTOR

C

0.1uF

BNC

VOUT

2

RLOAD

Setup

• Unpack the optical head, install a Thorlabs TR-series ½” diameter post into one of the #8-32 (M4 on /M version)

tapped holes, located on the bottom and side of the sensor, and mount into a PH-series post holder.

• Attach a 50Ω coax cable (i.e. RG-58U) to the output of the DET. Select and install a terminating resistor to the

remaining end of the cable and connect to a voltage measurement device. See the ‘Operation’ Section to
determine resistor values. Thorlabs sells a 50Ω terminator (T4119) for best frequency performance and a
variable terminator (VT1) for output voltage flexibility. Note the input impedance of your measurement device
since this will act as a terminating resistor. A load resistor is not necessary when using current measurement
devices.

• Power the DET on using the power switch. To check battery voltage, see ‘Battery Check’ below.

• Install any desired filters, optics, adapters, or fiber adapters to the input aperture. Caution: The DET10A was

designed to allow maximum accessibility to the photodetector by having the front surface of the diode flush with
the outside of the DET housing. When using fiber adapters, make sure that the fiber ferrule does not crash into
the detector. Failure to do so may cause damage to the diode and / or the fiber. An easy way to accomplish this
is to install a SM1RR retaining ring (included with the DET10A) inside the 1” threaded coupler before installing
the fiber adapter

• Apply a light source to the detector.

Battery Check and Replacement

Battery Check

Thorlabs new DET series includes a battery check feature that will allow the user to monitor the bias voltage on the
output BNC. Simply hold down the “VBIAS OUT” bottom located on the bottom edge of the unit. The bias voltage will
be output to the BNC. If a high impedance load is used (>10kΩ), the output will be equal to the bias voltage. This
feature includes a 1.05kΩ current limiting resistor (RCL) to prevent excessive loading of the battery if using small
terminating resistors. For example, a 50Ω load resistor with a 10V bias will produce a 200mA current without this
resistor. This will significantly decrease lifetime of the battery. The output bias voltage will be dependent on the load
resistor as described below. The A23 battery voltage characteristics show that the charge level is almost depleted as

13052-S01 Rev C 11/8/2011

Page 2 of 5

the voltage drops below 10V. For this calculation we assume 9.6V since VBAT = low battery voltage – one diode drop
(0.6V) = ~9V. The detector will continue to operate until the battery charge is completely drained, however these
numbers provide a reference point at which the battery should be replaced.

V

For V

= V

OUT

(min) = 9V, R

BAT

BAT

V

[R

OUT

/ (R

LOAD

LOAD

LOAD+RCL

= 50Ω, and RCL = 1050Ω

)]

= 410mV

BATTERY

PROTECTION

DIODE

VBAT

ON/OFF

+

RCL
1000

VBIAS OUT

PUSHBUTTON

SWITCH

RS
50

BNC

VOUT

RLOAD

Figure 3 – Battery Check Schematic

Battery Replacement

Thorlabs delivers each DET with an A23 12V battery installed. This battery is readily available at most retail stores, as
well as through Thorlabs. The battery supplied will deliver about 40 hours with a 1mA load, roughly equivalent to a
continuous 1.5mW light source at peak wavelength. The supply current when the unit is on and no light is applied is
very small and should not significantly degrade the battery.

Locate the battery cap directly above the output BNC. Unthread the cap and remove the battery. Install the new
battery into the cap, negative side in, and thread back into the DET. Be careful not to cross thread the cap into the
housing. The DET includes a protection diode to prevent damage if the battery is installed backwards. The battery
direction is located on the housing.

Troubleshooting

There is no signal response.

- Verify that the power is switched on and all connections are secure.

- Verify the proper terminating resistor is installed if using a Voltage measurement device.

- Verify that the optical signal wavelength is within the specified wavelength range.

- Verify that the optical signal is hitting the detector active area.

- Connect the DET to an oscilloscope without a terminating resistor installed. Most general purpose

oscilloscopes will have a 10MΩ input impedance. Point the detector toward a fluorescent light and verify that
a 60Hz (50Hz outside the US) signal appears on the scope. If so the device should be operating properly and
the problem may be with the light source or alignment.

There is an AC signal present when the unit is turned off.

The detector has an AC path to ground even with the switch in the OFF position. It is normal to see an output
response to an AC signal with the switch in this state. However, because the detector is unbiased, operation in this
mode is not recommended.

The output appears AC coupled with long rise times and the power switch ON.

This is usually an indication that the battery level is low and needs to be changed. See the Battery Check and
Replacement Section.

Maintaining the DET10A

There are no serviceable parts in the DET10A optical sensor. The housing may be cleaned by wiping with a soft
damp cloth. The window of the detector should only be cleaned using isopropyl alcohol and optical grade wipes. If
you suspect a problem with your DET10A please call Thorlabs and an engineer will be happy to assist you.

Contact

Americas

Thorlabs Inc.
435 Route 206 North
Newton NJ 07860
USA
Ph: [phone]
Fax: [phone]

www.thorlabs.com

Email:

[e-mail]

Europe

Thorlabs GmbH
Gauβstr. 11
85757 Karlsfeld
Germany
Ph: [phone]
Fax: [phone]

www.thorlabs.com

Email:

[e-mail]

UK and Ireland

Thorlabs, LTD.
1 Saint Thomas Place, Ely
Cambridgeshire CB7 4EX
Great Britain
Ph: [phone]
Fax: [phone]

www.thorlabs.com

Email:

[e-mail]

13052-S01 Rev C 11/8/2011

Page 3 of 5

Scandinavia

Thorlabs Sweden AB
Box 141 94
400 20 Göteborg
Sweden
Ph: [phone]
Fax: [phone]

www.thorlabs.com

Email:

[e-mail]

Japan

Thorlabs Japan, Inc
5-17-1, Ohtsuka
Bunkyo-ku,Tokyo 112-0012
Japan
Ph: [phone]
Fax: [phone]

www.thorlabs.jp

Email:

[e-mail]

WEEE

As required by the WEEE (Waste Electrical and Electronic Equipment Directive) of the European Community and the
corresponding national laws, Thorlabs offers all end users in the EC the possibility to return “end of life” units without
incurring disposal charges.

This offer is valid for Thorlabs electrical and electronic equipment

• sold after August 13th 2005

• marked correspondingly with the crossed out “wheelie bin” logo (see fig. 1)

• sold to a company or institute within the EC

• currently owned by a company or institute within the EC

• still complete, not disassembled and not contaminated

As the WEEE directive applies to self contained operational electrical and electronic products, this “end of life” take
back service does not refer to other Thorlabs products, such as

• pure OEM products, that means assemblies to be built into a unit by the user (e. g. OEM laser driver cards)

• components

• mechanics and optics

• left over parts of units disassembled by the user (PCB’s, housings etc.).

If you wish to return a Thorlabs unit for waste recovery, please contact Thorlabs or your nearest dealer for further
information.

Waste treatment on your own responsibility

If you do not return an “end of life” unit to Thorlabs, you must hand it to a company specialized in waste recovery. Do
not dispose of the unit in a litter bin or at a public waste disposal site.

Ecological background

It is well known that WEEE pollutes the environment by releasing toxic products during decomposition. The aim of the
European RoHS directive is to reduce the content of toxic substances in electronic products in the future.
The intent of the WEEE directive is to enforce the recycling of WEEE. A controlled recycling of end of live products
will thereby avoid negative impacts on the environment.

Crossed out “wheelie bin” symbol

13052-S01 Rev C 11/8/2011

Page 4 of 5

13052-S01 Rev C 11/8/2011

Page 5 of 5

0.60

15.2

2.10

53.3

2.76

70.1

1.70

43.2

1.89

48

0.535-40 INTERNAL THREAD
MATES WITH SM05 LINE

#8-32 x .25" THREAD
(M4 x 6.35MM for -EC VERSION)

1.03

26.2

0.75

19.1

POWER SWITCH

BATTERY DIRECTION INDICATOR

0.83

21.1

0.50

12.7

A

Battery Cap

OUTPUT BNC WITH

0 TO 10V RANGE

1.035-40 EXTERNAL THREAD
MATES WITH SM1 LINE

0.11

2.8

DETAIL A

SCALE 2 : 1

DETECTOR SURFACE

A

5

4

3

2

1

DET10A

MATERIAL:

PART NO.

TOLERANCES

PROPRIETARY AND CONFIDENTIAL

DIMENSIONS ARE IN INCHES
LINEAR TOLERANCES:

TWO PLACE DECIMAL:

0.010

THREE PLACE DECIMAL:

0.005

ANGULAR:

30'
SURFACE FINISH: 32 MICROINCHES
PARALLELISM: 0.002
FLATNESS: 0.002
STRAIGHTNESS: 0.002
CONCENTRICITY: 0.002
PERPENDICULARITY: 0.002
THREAD: CLASS 2 FIT

DRAWN
ENG APPR.
MFG APPR.

NAME

TITLE:

SIZE

A

REV.

SCALE: 1:1

SHEET 1 OF 1

13052-E01

THE INFORMATION CONTAINED IN THIS
DRAWING IS THE SOLE PROPERTY OF
THORLABS, INC. ANY REPRODUCTION
IN PART OR AS A WHOLE WITHOUT
THE WRITTEN PERMISSION OF
THORLABS, INC. IS PROHIBITED.

UNLESS OTHERWISE SPECIFIED:

DWG. NO.

EC
EC
EC

1/11/06

DATE

1/11/06
1/11/06

THORLABS INC.

PO BOX 366
NEWTON NJ

1mm Si BIASED DETECTOR

DET10A

COPYRIGHT

2006 by THORLABS INC.