The PDB Series

PDB140: DC to 15 MHz
PDB145: DC to 15 Mhz
PDB120: DC to 75 MHz
PDB110: DC to 100 MHz
PDB130: DC to 350 MHz
PDB150: Switchable Gain Version with Selectable Transimpedance Gain
PDB210: Fixed Gain Version with Large Sensor Area Optimized for Free Space Applications

Each model is available with either Si (-A) or InGaAs (-C) photodiodes and can also be ordered with AC coupling (-AC) to block any DC offset.

If you are interested in the developement of a 1.2 to 2.6 µm balanced detector, please take the time to learn about our prototype and fill out the survey.

Features

Total Wavelength Range for All Models: 320 - 1700 nm
Excellent Common Mode Rejection
High Bandwidth: DC to 350 MHz
Ultra Low Noise
Detector Types: Si & InGaAs
Free Space & Fiber Input
Direct Detector Monitor Outputs
Switchable Power Supply Included
Switchable Gain and Large Area Versions Available

Typical Applications

Spectroscopy
Heterodyne Detection
Optical Coherence Tomography OCT
Optical Delay Measurements
THz Detection

Functionality
The PDB100 and 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. Versions with different transimpedance gains, bandwidths and photodiodes are offered to suit a variety of applications.

Noise Reduction
The detectors of the PDB100 and PDB200 Series comprise two balanced photo detectors and an ultra-low-noise high-speed 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.

AC Coupled Version (-AC)
For blocking of the CW component (the unmodulated part) of the optical input signal an AC coupling version of the PDB Series is offered (for the BDB200 Series on request). This helps to improve the measurement capabilities in applications where it is desired to measure a comparably weak frequency modulated signal over a strong CW background signal, which could saturate the amplifier.

Connectors
Optical signals are coupled to the photodiodes for the PDB100 Series via two removable FC connectors while the PDB200 Series comes without fiber connector but with SM1 outer, and SM05 inner threads for fiber adapter mounting. This allows easy adaptation to either fiber coupled or free space applications. Three electrical connectors (SMA for the PDB100 Series and BNC for the PDB200 Series) 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
PDB100 Series and the PDB200 Series differ in detector size and housing style. Both are 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.

Model	PDB140A	PDB140C	PDB145A	PDB145C	PDB120A	PDB120C	PDB110A	PDB110C
Detector Type	Si/PIN	InGaAs/PIN	Si/PIN	InGaAs/PIN	Si/PIN	InGaAs/PIN	Si/PIN	InGaAs/PIN
WavelengthRange	320-1000nm	800-1700nm	320-1000nm	800-1700nm	320-1000nm	800-1700nm	320-1000nm	800-1700nm
Typical Max. Responsivity	0.53A/W	1.0A/W	0.53A/W	1.0A/W	0.53A/W	1.0A/W	0.53A/W	1.0A/W
Active Detector Diameter	0.8mm	0.3mm	0.8mm	0.3mm	0.8mm	0.3mm	0.8mm	0.3mm
Bandwidth (3dB)	DC-15MHz				DC-75MHz		DC-100MHz
Common Mode Rejection Ratio	>35dB		>35dB		>35dB		>25dB (typ. > 35dB)
Transimpedance Gain¹	560 x 10³V/A		51 x 10³V/A		180 x 10^3 V/A		50 x 10^3V/A
Conversion Gain RF-Output	297x 10³V/W	560 x 10³V/W	27 x 10³V/W	51 x 10³V/W	95 x 10^3V/W	180 x 10^3V/W	2.65 x 10^4V/W	5 x 10^4V/W
Conversion Gain Monitor Outputs	100V/mW @ 820nm	100V/mW @ 1550nm	100V/mW @ 820nm	100V/mW @ 1550nm	10V/mW @ 820nm	10V/mW @ 1300nm	10V/mW @ 820nm	10V/mW @ 1550nm
CW Saturation Power RF-Output	12µW @ 820 nm	6.5µW @ 1550nm	130µW @ 820 nm	70µW @ 1550nm	38µW @ 820nm	20µW @ 1300nm	130µW @ 820nm	70µW @ 1550nm
Minimum NEP (DC-10MHz)	5.7pW/Sqrt(Hz)	3.2pW/Sqrt(Hz)	5.7pW/Sqrt(Hz)	3.2pW/Sqrt(Hz)	6pW/Sqrt(Hz)	3.2pW/Sqrt(Hz)	6.9pW/Sqrt(Hz)	3.6pW/Sqrt(Hz)
Optical Inputs²	FC/PC or FC/APC (Removable)
Photodiode Damage Threshold	20mW
Electrical Outputs	SMA
RF-Output Impedance	50W
RF-Output Coupling	DC, AC-Coupling upon Request
Size	85 x 80 x 30mm
Power Supply	± 12V @ 200mA

Model	PDB130A	PDB130C	PDB150A	PDB150C	PDB210A	PDB210C
Detector Type	Si/PIN	InGaAs/PIN	Si/PIN	InGaAs/PIN	Si/PIN	InGaAs/PIN
Wavelength Range	320-1000 nm	800-1700 nm	320-1000 nm	800-1700 nm	320-1060 nm	800-1700 nm
Typical Max. Responsivity	0.50A/W	1.0A/W @ 1550 nm	0.53A/W	1.0A/W	0.6A/W @ 920 nm	1.0A/W @ 1550 nm
Active Detector Diameter	0.4 mm	0.15 mm	0.8 mm	0.3 mm	5 mm	3 mm
Bandwidth (3dB)	DC-350 MHz		DC-150, 50, 5, 0.3, 0.1 MHz		DC-1 MHz
Common Mode Rejection Ratio	>20 dB (typ. > 25 dB)		>25 dB (typ. > 30 dB)		40 dB	30 dB
Transimpedance Gain1	10 x 10^3 V/A		10^3, 10^4, 10^5, 10^6, 10^7 V/A		500 x 10^3 V/A 175 x 10^3 V/A with 50 Ω Termination
Conversion Gain RF-Output (V/W)	5 x 10^3	10 x 10^3	0.53x10^3, 0.53x10^4, 0.53x10^5, 0.53x10^6, 0.53x10^7	10^3, 10^4, 10^5, 10^6, 10^7	300 x 10^3	500 x 10^3
Conversion Gain Monitor Outputs	10 V/mW @ 820 nm	10 V/mW @ 1550 nm	10 V/mW @ 820 nm	10 V/mW @ 1550 nm	10 V/mW @ 920 nm	10 V/mW @ 1550 nm
CW Saturation Power RF-Output	700 µW @ 820 nm	400 µW @ 1550 nm	10 mW @ 820 nm	5 mW @ 1550 nm	33 µW @ 920 nm	20 µW @ 1550 nm
Minimum NEP (DC-10 MHz) (DC-1 MHz For PDB200 Series)	14.7 pW/Sqrt(Hz)	7.4 pW/Sqrt(Hz)	0.6 pW/Sqrt(Hz)	0.3 pW/Sqrt(Hz)	2.2 pW/Sqrt(Hz)	16 pW/Sqrt(Hz)
Optical Inputs2	FC/PC or FC/APC (Removable)
Photodiode Damage Threshold	20 mW
Electrical Outputs	SMA				BNC, 100Ω
RF-Output Impedance	50 W
RF-Output Coupling	DC, AC-Coupling upon Request
Size	85 x 80 x 30 mm				83.9 mm x 53.4 mm x 21 mm
Power Supply	± 12V @ 200 mA

¹ Transimpedance Gain is reduced by a factor of two for 50Ω loads
² For Model PDB130C FC adapter is NOT removable

The Thorlabs PDB100 and 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 photodiodes, (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 separately. These outputs are low frequency outputs and cannot be used to measure an RF modulation on the signal.

Balanced receiver

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

Balanced Amplified Photodetector
Power Supply
Adapter Plate
Operating Manual

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Posted Comments:
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?