Typical Applications

Spectroscopy
Heterodyne Detection
Optical Coherence Tomography
Optical Delay Measurements
THz Detection

Features

Large Active Areas for Free-Space Beams
Three Models

190 - 1100 nm (UV Enhanced Al)
320 - 1060 nm (Si)
800 - 1700 nm (InGaAs)

Excellent Common Mode Rejection
High Bandwidth: DC to 1 MHz
Ultra Low Noise
Detector Types: Si or InGaAs
Designed for Free-Space Applications (Fiber Input Also Feasible)
Direct Detector Monitor Outputs
Switchable Power Supply Included
External SM1 Threads and Internal SM05 Threads

These Balanced Amplified Photodetectors utilize two well-matched large-area Si or InGaAs detectors and an ultra-low noise transimpedance amplifier to detect signal path differences in two beams. An output voltage (RF-OUTPUT) is generated that is proportional to the difference between the photocurrents in the two photodiodes (i.e., the two optical input signals). Additionally, the unit has two fast monitor outputs (MONITOR+ and MONITOR-) to measure optical input power levels as well as RF modulated signals on each detector.

The detectors are spaced 2" apart, making beam alignment an easy task on an optical table. To further simplify the use of these detectors, the housing has external SM1 (1.035"-40) and internal SM05 (0.535"-40) threads around each detector to attach components such as lens tubes, cage systems, mounted optics, and fiber adapters.

Functionality
The PDB200 Balanced Detector Series act as a balanced receiver by subtracting the two optical input signals from each other resulting in the cancellation of common mode noise. This allows small changes on the signal path to be extracted from the interfering noise floor.

Noise Reduction
These balanced amplified photodetectors are comprised from two balanced photodetectors and an ultra-low-noise transimpedance amplifier. The intelligent design of these devices allow an improved matching of the two balanced photo detectors to achieve an excellent common mode rejection, leading to better noise reduction. Please see the Operation Tab for more details.

Connectors
The optical signal inputs are free space for the PDB200 Series, but the items do feature external SM1 (1.035"-40), and internal SM05 (0.535"-40) threads for fiber adapter mounting. This allows easy adaptation to either fiber coupled or free space applications. Three electrical BNC connectors provide the balanced output signal plus a power monitor for each of the two input signals. These two monitors enable the control of the input power levels and can be used as an independent power meter for each channel.

Packaging/Power Supply
The PDB200 Series is housed in a rugged, shielded aluminum enclosure. The housing allows a mounting post adapter to be fixed to the bottom or side surface by 8-32 (M4) screws. The unit is powered from a ±12 V DC power supply which is provided with the unit. The input voltage of 110 V or 230 V can be manually selected by a switch.

Thorlabs also offers Fiber-Based Interferometers, which feature an integrated balanced detector.

Item #	PDB210A2	PDB210A	PDB210C
Detector Type	UV Enhanced Si/PIN	Si/PIN	InGaAs/PIN
Wavelength Range	190 - 1100 nm	320 - 1060 nm	800 - 1700 nm
Typical Max Responsivity	0.5 A/W @ 960 nm	0.6 A/W @ 920 nm	1.0 A/W @ 1550 nm
Active Detector Diameter	4.1 mm	5 mm	3 mm
Bandwidth (3 dB)	DC-1 MHz
Common Mode Rejection Ratio	Min 30 dB, Typical 40 dB	40 dB	30 dB
Transimpedance Gain	500 x 10³ V/A 175 x 10³ V/A with 50 Ω Termination
Conversion Gain RF-Output (V/W)	250 x 10³	300 x 10³	500 x 10³
Conversion Gain Monitor Outputs	10 V/mW @ 960 nm	10 V/mW @ 920 nm	10 V/mW @ 1550 nm
CW Saturation Power RF-Output	40 µW @ 960 nm	33 µW @ 920 nm	20 µW @ 1550 nm
Minimum NEP (DC-1 MHz)	2.4 pW/Sqrt (Hz)	2.2 pW/Sqrt (Hz)	16 pW/Sqrt (Hz)
Optical Inputs	Freespace
Photodiode Damage Threshold	20 mW
Electrical Outputs	BNC, 100 Ω
RF-Output Coupling	DC, AC-Coupling upon Request
Dimensions (H x W x L)	85.3 mm x 65.3 mm x 21.1 mm (3.36" x 2.57" x 0.83")
Power Supply	±12 V @ 200 mA

PDB200 Series

Monitor +/-

BNC Female

0 - 10 V Hi-Z (1.5 V for 50Ω loads)

RF Output

BNC Female

±10 V for Hi-Z (±3 V for 50 Ω loads)

Thorlabs' PDB200 Series Balanced Amplified Photodetectors consist of two well-matched photodiodes and an ultra-low noise, high-speed transimpedance amplifier (TIA) that generates an output voltage (RF OUTPUT) proportional to the difference between the photocurrents in the two photodiode (i.e., the two optical input signals). Additionally, the unit has two monitor outputs (MONITOR+ and MONITOR-) to observe the optical input power levels on each photodiode.

Balanced receiver

The following parts are included together with each of our Balanced Amplified Photodetectors:

Balanced Amplified Photodetector
Power Supply
Operating Manual

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Posted Comments:

Poster: lukasz.piatkowski

Posted Date: 2012-10-09 11:21:31.143

Could you provide temporal response information for the balanced PDB210A/M photodiode? What is the raise time? Kind regards.

Poster: jvigroux

Posted Date: 2012-04-20 08:52:00.0

A response from Julien at Thorlabs: thank you for your inquiry! In order to be able to to help suggesting some appropriate settings, we would need some more information concerning your exact experimental setup. I will contact you directly to discuss this point.

Poster: g.karaoglan

Posted Date: 2012-04-19 16:07:34.0

I want to use the photodetector for THz applications but I can not detect a signal yet. The best I can decrease the RF output down to microvolts order on the lock in but I can not make sure if it is enough to say it is balanced (PC generatin-EO detection with ZnTe crystal) Is there a chopper frequency you can suggest that yields a good SNR? Any other suggestions that may help me to find a signal? Thanks!

Poster: bdada

Posted Date: 2012-02-14 13:37:00.0

Response from Buki at Thorlabs to alsturl: Thank you for using our feedback tool. All the outputs for the Balanced Photodetector are grounded.

Poster: alsturl

Posted Date: 2012-02-13 21:22:07.0

Is the RF output shield floating or grounded? Thanks!

Poster: jvigroux

Posted Date: 2012-01-18 12:14:00.0

A response from Julien at Thorlabs: Thank you for your inquiry. This detector unfortunately does not have an auto-balance function such that it is indeed necessary to balance the two channels manually.

Poster: jean-paul.booth

Posted Date: 2012-01-18 10:23:24.0

Does this unit include auto-balancing? Or is it necessary to manually adjust the light intensity on one channel?

Poster: jvigroux

Posted Date: 2011-06-09 16:48:00.0

A response from Julien at Thorlabs: Dear Romain, the PDB210A has an analog output that delivers a voltage of maximum 10V. this type of voltage can usually be acquired quite conveniently by data acquisition cards such as those offered by national instruments. This type of approach is probably the most suited to the acquisition of large amount of data. To further discuss your application, please do not hesitate to contact our tech support at techsupport@thorlabs.com

Poster: romdu126

Posted Date: 2011-06-07 17:52:13.0

Dear Mister, Madam, I just received the product PDB210A/M, it looks great and I hope it will perform well. My question will be very simple and I apologize for that since I am still a beginner with pratical experiments. I would like to perform Surface Plasmon Resonance measurements, therefore make a whole bunch of data measurements, lets say hundred different angles for one experiment. I would like to collect the value of the intensity measured on a computer and export them in a .dat file. What would be then the easiest solution for me? Using Labview or some sort of similar software ? What do people usually use to collect information on a massive scale, when handling your detector ? Thanks in advance for your answer. Best regards, Romain Dubreuil

Poster: jjurado

Posted Date: 2011-05-03 11:43:00.0

Response from Javier at Thorlabs to last poster: Thank you very much for your feedback. We have corrected this information on the web.

Poster:

Posted Date: 2011-05-03 10:52:07.0

*Ohms

Poster:

Posted Date: 2011-05-03 10:51:48.0

RF output impedance from the Specs tab should be 50 O, rather than 50 W.

Poster: Thorlabs

Posted Date: 2011-01-18 09:10:55.0

Response from Javier at Thorlabs to last poster: Thank you very much for your feedback. We have updated the web presentation of the bandwidth spec for the PDB150 according to your suggestion.

Poster:

Posted Date: 2011-01-17 22:24:34.0

bandwidth specification for the PDB150 is a little confusing. Typically it would be specified in increasing order. so here it should be DC-0.1, 0.3, 5, 50, 150 MHz and not DC-150, 50, 5, 0.3, 0.1 MHz.

Poster: julien

Posted Date: 2010-04-06 11:10:29.0

a response from Julien at Thorlabs: The plastic is needed to prevent the apparition of ground loops that would severely reduce the measurement accuracy. We cannot simply replace it with aluminum or if we do so, the detector then needs to be mounted on an insulating post. We are currently looking at other materials to replace the plastic used at the moment.

Poster:

Posted Date: 2010-04-03 17:33:21.0

I do not agree that plastic makes a reasonable mounting plate for any optomechanical device, especially not one selling for more than $1000. Please change this plate to aluminum.

Poster: julien

Posted Date: 2010-04-01 10:32:15.0

A response from Julien at Thorlabs: Thank you for your valuable feedback. The plastic plate is sufficient for most applications but you are absolutely right about the fact that it can only withstand so much. I will contact you directly to see if we can find an easy solution to your problem.

Poster: gidiloo

Posted Date: 2010-03-31 20:30:49.0

Please dont make the mounting plate out of plastic. Its ridiculous. Make it durable. If you need to screw something tight, the plastic is not even a bad joke. Thanks.

Poster: apalmentieri

Posted Date: 2010-02-24 13:20:03.0

A response from Adam at Thorlabs to lsandstrom: There is internal SM05 and SM1 threads on the PDB210A. Therefore, you can use both 1" or 1/2" mounted ND filters with this device.

Poster: lsandstrom

Posted Date: 2010-02-24 11:22:32.0

Is there an external or internal SM1 thread on the detector? The picture in the manual seems to be different from the Photo on the webpage. What mounted ND filters should i use together with the detector 1" or 1/2"?

Poster: apalmentieri

Posted Date: 2010-02-18 09:33:57.0

A response from Adam at Thorlabs: The catalog is correct, the power supply provided is switchable. We will update the webpage to reflect this information. Thanks for bringing this to our attention.

Poster:

Posted Date: 2010-02-18 04:26:56.0

It says that all the PDB1XXA/AC compatible for 110 VAC . on the other hand the catalog page says (1294 V.20) that there is a SWITCHABLE POWER SUPPLY INCLUDED: 110 VAC ,230 VAC. which is more accurate?

Poster: klee

Posted Date: 2009-11-06 17:52:48.0

A response from Ken at Thorlabs to acable: The BW of DC-10 MHz is for the PDB100 series. For the PDB200 series, it should be DC to 1MHz instead. This has been added to the specifications.

Poster: acable

Posted Date: 2009-11-06 17:15:29.0

The PDB210A is specified as having a NEP of 2.2 pW/Sqrt(Hz) with a side note indicating this number is based on a BW of DC to 10 MHz, however the detector package has a bandwidth of only 1 MHz. Is this a simple typo or am i missing something.

Poster: jens

Posted Date: 2009-08-05 11:58:30.0

A reply from Jens at Thorlabs: since this is a specific application I will get you in contact with the engineer who is focussing on this part.

Poster: max.abashin

Posted Date: 2009-08-04 16:35:52.0

I am quite interested in using a balanced detector for heterodyne detection. But I am not sure how to arrange the scheme. Suppose Asig - magnitude of optical field in the signal arm and Aref - in the reference arm, which is frequncy shifted by 10 kHz. Aref>>Asig (which is on the order of 10fW .. 1pW in our case), so the usual photodetector has voltage proportional to Aref^2+Aref*Asig, first term is DC and the second is AC (10 kHz modulation), of course we are interested in recovering Asig from AC so Lock in detection referenced by 10 kHz is used. Now, there are two solutions for implementing balanced detection can be found. First (Opt. Expr. 16, 494), where one of the detectors is fed with interfering mixed signal and the other one with the reference tap. Second (Opt. Lett. 21, 1427), where both detectors are fed with the interfering signal from the same beam splitter and thus have similar sinusoid but possibly phase shifted. Which one you have in mind in your applications list? Also, should AC or DC coupling be used (on the one hand we do not need quite strong DC), but what is the time constant of filtering? And also it is not that hard to attenuate non-modulated reference if the first scheme is used.

Poster: jens

Posted Date: 2009-07-01 08:29:37.0

A reply from Jens at Thorlabs: I discussed the design with the team and the exact location of the capacitor in the block diagram is before the TIA in front of the RF port. With this the DC component will not get amplified and you can avoid saturation of the amplifier. You can still use a filter outside based on a DC detector version but saturation of the amplifier may limit the performance of such a setup.

Poster: jens

Posted Date: 2009-06-30 13:57:29.0

A reply from Jens at Thorlabs: the coupling would be located next to the RF output port in the block diagram on page 15. In principle you could add your own filter to a DC version I think but since that filter needs to fit to the internal design of the PDB you would probably run into trouble with for example cut off frequency, temperature dependencies etc. I will request additional information from the design engineer and add.

Poster: john.a.krawczak

Posted Date: 2009-06-30 13:35:19.0

I am considering an AC coupled version. I have the user guide which shows a block diagram on page 15 and AC coupling discussion on page 36. Where is the capacitor put for AC coupling in the block diagram of page 15? Can I just use a bullet SMA capacitor at the output of the DC coupled version and get the same thing if I want AC?

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Large-Area Balanced Amplified Photodetectors

Typical Applications

Features

PDB200 Series

Monitor +/-

BNC Female

RF Output

BNC Female