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Position Sensing Detectors

  • Quadrant and Lateral Effect Sensors
  • Compact Footprint
  • Compatible with SM05 Lens Tubes


2D Lateral 
Effect PSD


Quadrant PSD


T-Cube Controller

Sensor and Controller
Sold Separately

Related Items

Lateral Effect Position Sensor

Click Image to Zoom
Item #PDP90A
Wavelength Range 320 to 1100 nm
Resolution, @ 635 nm <0.68 µm @ 100 µW,
<6.8 µm @ 10 µW
Noise <2.25 µmpp, 340 nmrms
Recommended Spot Size Ø0.2 – 7 mm

PDP Operating Power Chart

The shaded area in the chart above shows the min and max input power levels as a function of wavelength. Make sure the incident beam power is as close to the max level for the best resolution and noise figure possible. Going over the max level will saturate the sensor and give erroneous results.


  • Lateral Effect Position-Sensing Detector
  • Insensitive to Beam Shape and Power Density
  • SM05 Lens Tube Compatible
  • Compact Footprint

The PDP90A Position Sensor utilizes a pincushion tetra lateral sensor to accurately measure the displacement of an incident beam relative to the calibrated center. These devices are ideal for measuring the movement of a beam, the distance traveled, or as feedback for alignment systems. 

The large detection surface allows a beam diameter of <9 mm, however, our recommended range is 0.2 to 7 mm. Unlike quadrant sensors which require overlap in all quadrants, the lateral sensor will provide positional information of any spot within the detector region, independent of beam shape, size and power distribution. The PDP90A has a very low noise figure of <2 mVpp (<300 µVrms), which corresponds to a detection error of 0.675 μmrms. Resolution is directly related to the optical input power by the following equation,

PDP90A Equation 3

ΔR is the Resolution,
Lx is the detector length, 10 mm,
en is the output noise voltage, <300 µVrms, and
Vo is the Sum output voltage level, 4 V max.

Therefore, for the maximum power level, the resolution will be 0.675 µm. More detailed technical information can be found on the Tech Info tab.

Each PDP90A lateral position-sensing detector is packaged with a 8-32 to M4 adapter to provide compatibility with either imperial or metric mounting posts. A controller, TPA101, is available separately below.

PDP Responsivity
Item #PDP90A
Electrical Specification
Wavelength Range320 to 1100 nm
Peak Responsivity0.6 A/W @ 960 nm
Resolutiona0.675 µm
Voltage Noiseb<2 mVpp, <300 µVrms
Displacement Noise<2.25 µm
Transimpedance Gain100 kV/A
Max Photocurrent40 µA
Output Voltage Range±4 Vmin
Signal Output Offset0.3 mVtyp (7 mVmax)
Bandwidth15 kHz
Recommended Spot SizecØ0.2 – 7 mm
Maximum Spot SizedØ9 mm
Supply Voltage Requirement±5VDC ± 5%, 35 mA
Operating Temperature10 to 40 °C
Storage Temperature-20 to 80 °C
Physical Specifications
Sensor Size9 mm x 9 mm
(0.35″ x 0.35″)
Clear ApertureØ0.50″ (Ø12.7 mm)
Aperture ThreadSM05 (#0.535-40)
Dimensions2.00″ x 1.20″ x 0.65″
(50.8 x 30.5 x 16.5mm)
Mounting Thread#8-32 x 0.25″ min depth
Metric AdapterM4 to #8-32 Adapter (Part No AS4M8E)
Cable Length, Typical5′ (1.5 m)
Connector (Plug)Hirose HR10A-7P-6P
Mating ReceptacleHirose HR10A-7R-6S
Weight0.25 lbs (114 g)
  • Resolution is dependent on input optical power. Specification assumes photocurrent is 40 µA.
  • Across whole 15 kHz bandwith of detector.
  • Spots smaller than 0.2 mm could increase the position detector error.
  • Specified at the waist of the pincushion.
    PDP Resolution Equation

2D Lateral Effect Position-Sensing Detectors


PDP90A Lateral Effect Sensor Diagram

The 2D lateral effect sensors provide an accurate way to measure displacement - movements, distances, or angles – as well as feedback for alignment systems such as mirror control, microscope focusing, and fiber launch systems. These sensors work by proportionally distributing photocurrent using resistive elements to determine position and are usually referred to as lateral effect sensors. There are two different types of lateral effect sensors available Duo lateral and Tetra lateral.

Duo lateral sensors provide a resistive layer on both the anode and cathode photodiode connections. This isolates the x and y positional information of the sensor and allows the sensor to be highly linear and very accurate. However, the added resistive layers significantly increase manufacturing cost.

Tetra lateral sensors use a single resistive layer with a common cathode and an anode on each side of the detection area. This makes them very inexpensive to manufacture, however the linearity decreases as the spot moves away from the center. This is caused by the physical location of the anodes along the sides of the sensor, specifically in the corners where the anodes approach each other. Thorlabs uses a variation of the Tetra lateral sensor commonly called a “pin cushion” sensor. This sensor moves the anodes to the four corners of the sensors and reshapes the sensor area, to produce linearity comparable to a duo lateral sensor at a significantly lower cost.

Calculating the Position

The PDP90A includes circuitry to decode the Dx, Dy, and SUM signals as follows:

PDP Equation 4

From these formulas, the actual distances can be calculated with the following equations:

PDP Equation 5

Where x and y are the distances from the center of the sensor. Lx and Ly are the resistance lengths of the active sensor region. For the PDP90A sensor, these values are Lx = Ly = 10 mm.

Positional Errors

Unlike quadrant style photodiodes, lateral effect sensors are independent of beam shape and size. They will provide positional information of the centroid of the spot as long as the light is located on the sensor. If part of the light moves off the sensor, it will cause a shift in the centroid making the beam measurement unreliable.

Positional errors will also be caused by ambient light levels. For best results the PDP90A should be operated in a dark location. However, light baffling using lens tubes and irises to narrow the field of view (FOV) will limit ambient light level errors.

Position Resolution

PDP Application shot
Photo of a PDP90A sensor with 2 SM05L10 Lens Tubes
and 1 SM05D5 Iris

Position resolution is the minimum detectable displacement of a light spot incident on the PSD. Position resolution (ΔR) is a factor of both the resistance length (Lx or Ly), or the x and y length, and the signal to noise ratio (S/N). The signal to noise ratio for this system can be defined as the SUM output signal level (Vo) divided by the output voltage noise (en). The PDP90A output noise is <2 mVpp, or <300 µVrms.

PDP Equation 3

ΔR is the Resolution,
Lx is the detector length,
en is the output noise voltage, and
Vo is the Sum output voltage level.

For the PDP90A:

PDP Equation 6

For best results Vo should be maximized to 4 V resulting in a position resolution of 0.675 µm. To do this, monitor the SUM output voltage of the sensor and adjust the optical intensity until the output is approximately 4 V. Increasing above 4 V will saturate the system causing unreliable readings. The provided operational software will indicate the voltage level on a slide bar. If the SUM is saturated the slide bar color will turn red. Back off the intensity until it switches to green. This will be equivalent to a 4 V SUM output.

Photodiode Detail

Photodiode Detail

Detector Out - HIROSE

HiRose Out

1X-axis [A + C] - [B + D]
2Y-axis [A + B] - [C + D]
3SUM [A + B + C + D]
4+Vsupply (+5 V)
6-Vsupply (-5 V)
PDP90A SmartPack Packaging
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PDP90A Packaging

Smart Pack

Item #% Weight
PDP90A 34.45% 13.66 kg
PDQ80A 34.45% 9.87 kg

Smart Pack

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Thorlabs' Smart Pack Initiative is aimed at waste minimization while still maintaining adequate protection for our products. By eliminating any unnecessary packaging, implementing packaging design changes, and utilizing eco-friendly packaging materials for our customers when possible, this initiative seeks to improve the environmental impact of our product packaging. Products listed above are now shipped in re-engineered packaging that minimizes the weight and the use of non-recyclable materials.b As we move through our product line, we will indicate re-engineered packages with our Smart Pack logo.

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Click the Support Documentation icon document icon or Part Number below to view the available support documentation
Part NumberProduct Description
PDP90A Support Documentation PDP90A:2D Lateral Effect Position Sensor, 320 to 1100 nm

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Posted Comments:
Posted Date:2015-04-08 08:15:49.0
Response from Mike at Thorlabs: Quadrant detectors are used primarily for beam alignment whereas lateral effect sensors are normally used for position measurement. However, the TPA101 can be used with either type of sensor for both auto-alignment and position measurement. Both types of sensor output three voltages (XDiff, YDiff and SUM) that are proportional to the position of the beam and the total optical power, however, lateral effect sensors like the PDP90A have a defined accurate relationship between these three voltages. Furthermore, if the user selects the PDP90A sensor type in the settings panel in the APT USER software the displays shows the XPos and YPos values in millimeters, whereas if the PDQ80A or PDQ30C sensor type is selected, the display shows the XDiff and YDiff values that the sensor outputs in Volts. The TPA101 always reads the voltages, but additionally for the PDP90A sensor, it is capable of calculating the exact X, Y position from these voltages.
Posted Date:2015-04-02 10:13:51.85
We have the PDP90A connected to the TPA101 and illuminate the PDP90A with a laser beam. The software does not display the numerical X-Y position of the beam! It only displays a graphical representation. I see one other poster having the same problem from a couple of years ago. Is there a solution?
Posted Date:2015-02-24 04:17:56.0
Response from Jeremy at Thorlabs: The detector should be able to differentiate between each pulse because of the rep. rate relatively low so it won't be a continuous signal. I will contact you directly to discuss about your application.
Posted Date:2015-02-12 13:35:57.113
Hello, I am interested in using this sensor for pointing stabilization for a ~40 fs, 780nm pulse with a 1 kHz rep rate. Would this detector give a continuous signal for the beam position, or would it be choppy because of how short the pulse is?
Posted Date:2015-01-30 04:54:10.0
Response from Jeremy at Thorlabs: The PDP90A is assembled in USA.
Posted Date:2015-01-29 21:15:47.02
Please advise part number : PDP90A product made in country ????? Suntaree Yuenyongwattanakorn Inhouse Sales Section Head Globaltronic Intertrade Co., Ltd. 634/2 Soi Ramkhamhaeng 39 (Thepleela1), Wangthonglang, Bangkok 10310, Thailand HP : 08-5480-1464 TEL : 0-2530-9099 (Auto), 0-2935-6799 (Auto) ext. 213 FAX : 0-2935-6790,0-2530-9077
Posted Date:2014-06-03 02:33:51.0
A response from Bweh at Thorlabs in Newton-USA: Thanks for contacting Thorlabs. The recommended impedance is >=10kohm.
Posted Date:2014-05-28 13:22:42.24
I see in some past comments that other customers were interested in accessing signals from the detector without the controller. I'm interested in the PDP90A - could you give recommendations on what input impedance I should have to read signals from the PDP90A in the absence of a TPA101 controller? Thanks.
Posted Date:2013-08-18 09:47:18.603
I'd like to use the PDP90A with a 1 Watt Q-switched 355 nm laser with 30 microJoule per pulse and a rep rate of 30 kHz. Is there an issue of using the detector with a pulsed laser or does it just average? I would like to monitor the position of the beam after going through a lens. I will place the sensor after the beam has gone through focus - so the spot size can be set to optimum - but the beam will not be collimated - is that an issue? Thanks
Posted Date:2013-09-17 15:18:00.0
Response from Jeremy at Thorlabs: A 1W laser would be too powerful for the PDP90A and you can damage the detector. Typically if the repetition rate of your source is a lot higher than the bandwidth of the detector (15kHz in the case of PDP90A), then the detector would just average out the signal and it should still be able to give you the position information. We will contact you directly to discuss about this further.
Posted Date:2013-08-05 23:11:35.067
PDP90A Recommended spot size 0.2mm-7mm. Can I use a smaller spot size? Is there any issue?
Posted Date:2013-08-08 14:55:00.0
Response from Phong at Thorlabs: We recommend using a spot size > 0.2 mm, since a smaller spot size could increase the the position detection error.
Posted Date:2013-07-16 20:04:00.0
Response from Tim at Thorlabs: The rise time is ~2.3*10^-5 seconds.
Posted Date:2013-07-10 14:14:50.71
What is the typical rise time for this detector?
Posted Date:2013-03-07 21:27:29.993
Is there a way to read a physical position using this detector? We just purchased it, but it looks like the provided software only gives a voltage differential when we illuminate the detector with a laser. It is important for our application that we be able to measure the x-y coordinates of the beam.
Posted Date:2013-03-12 12:59:00.0
Response from Jeremy at Thorlabs: You could use the PDP90A to read the position. This information can be found under the "Tech Info" tab on the PDP90A page (
Posted Date:2012-02-24 10:33:00.0
Response from Tim at Thorlabs: The output signal can be recorded with a NI DAQ card. You will need some software for controlling the card, but you will not need any software from us. If you have any further questions, you can contact us directly at
Posted Date:2012-02-22 22:49:27.0
Can TQD001 output signal (LV OUT XDIFF\YDIFF \SUM) receive by NI DAQ card (Analog receiver) without any software?
Posted Date:2012-02-21 16:30:00.0
Response from Tim at Thorlabs: When used with the TQD001 control module the position sensing detectors can be run with our APT software. By clicking on the red page icon next to the TQD001 product number, you can view the manual which has information on the software and the methods for use with LabVIEW. You can also view the manual at The SPLICCO software, our standard software package for spectrometers and line cameras, is not needed for use with the position sensing detectors. The SPLICCO software is located at and the APT software for use with the TQD001 and our position sensing detectors can be located at
Posted Date:2012-02-21 04:32:37.0
Is there any Versatile Software Package (Splicco) and Drivet Package (""""For LabVIEW"""")
Posted Date:2011-12-13 20:23:00.0
Response from Buki at Thorlabs: A 10m cable will work but we do not have any performance data for various lengths. Please contact if you have additional questions.
Posted Date:2011-11-18 09:35:22.0
is there a limitation on cable length for the distance between the PDP90A and the TQD001? If we extend the cable to 10m, what will happen to the signal integrity/strength?
Posted Date:2011-11-02 18:18:00.0
Response from Buki at Thorlabs: Thank you for your feedback. We are currently redesigning these detectors to include access to each of the output signals (x, y, and sum) through SMC connectors. We will contact you to provide more information.
Posted Date:2011-11-01 20:27:31.0
A breakout cable or adapter with provides signal outputs on BNC connectors would be very useful. The controller is not needed in our application.
Posted Date:2011-09-15 17:12:05.0
On the PDP90A how good is the linear response to the displacements? That is, how far from the detector center can I have the ray and still use the linear approximation. Thx.
Posted Date:2011-08-08 11:54:00.0
Response from Javier at Thorlabs to cchipman: The distance between the active area of the PDP90A and the front plane of the housing is 3.5+/-0.5 mm.
Posted Date:2011-08-05 13:31:58.0
The depth of the detector within the housing for the PDP90A is not detailed in your drawing (At least that I can find). What is it?
Posted Date:2011-01-11 11:04:13.0
A response from Greg at Thorlabs to infante.cristian: I apologize for the delay in getting back to you. An applications engineer will be in contact with you shortly to discuss centroid detection.
Posted Date:2010-12-31 01:45:28.0
Im new in optical applications, and i need to calculate the beam centroid with PDP90A. For my application, i will integrate (approx. 10Hz) and sample the outputs, i think that this will decrease error for my application (alignment and tracking) but im not sure. lease mail me to discuss this and other products for centroid detection. Thanks!
Posted Date:2010-08-10 23:51:57.0
Response from Javier at Thorlabs to kvasnicka: Thank you for your feedback. A1: The 300 uVrms noise figure is guaranteed over the entire bandwidth of the detector (15 kHz). In reality, the noise is much lower, but we keep this conservative value based on the noise floor of our oscilloscope (HP Infinium 1.5GHz). The total calculated noise values are approximately 51 uVrms (I will send you Excel files with calculations and data). A2: At 1 Hz, the total noise decreases to about 0.41 uVrms. A3: At max. optical power, the detector and amplifier circuits are saturated by high input intensity, compromising the reliability of the measured signal. A4: The PDP90A is not shot-noise limited. In reality the environmental noise should be more of a problem. Laser intensity noise could add to the overall performance, however simultaneously sampling all 3 outputs should minimize this. Background light will certainly add to the errors but in most cases this can be dealt with. Temperature is a larger problem. Ambient temperature changes will affect the accuracy of the readings. The sensor is made up of a standard large area Si photo detector mounted to a resistive subsurface. The position information is distributed to the 4 corners of the sensor based on this proportional resistance to each corner. Temperature changes can affect this resistive network and move the relative position. The worst case occurs when there are temperature gradients across the sensor. Sealing the sensor from air flows will improve this. How well the ambient temperature is controlled will also have an effect. For digitizing the output, if you were to use a 16 bit A/D card set to a +/-5V input range, the 1 bit resolution is 10V/2^16 = ~150uV. Notice that the calculated values of the noise are less than the resolution of the A/D. Our safe number of 300uV is approximately 2 bits of noise in a 16 bit A/D. This is better than what most cards can specify. For better resolution there are 20 bit cards available.
Posted Date:2010-07-02 10:39:24.0
Response from Javier at Thorlabs to thank you for your feedback. The main purpose of the application idea is to show the type of components that you could potentially need to create an active auto-alignment setup for applications in which experimetal results are highly dependent on the alignment of the laser with respect to the optics. There are many factors that contribute to the loss of alignment of a laser in a setup, most of which you mentioned. Thermal drift is perhaps one of the main effects. You can have environmental thermal drift, which can affect the mounting mechanics of the laser (most mounting optomechanics use Aluminum as the main material, which has a high coefficient of thermal expansion), or internal thermal effects that affect the beam pointing stability of the laser. This can be critical in application such as fiber coupling. Also, mechanical vibrations can have negative effect in many experiments, which can be corrected for by using a quadrant or lateral effect sensor. I will contact you directly to discuss your application and the possible uses of these alignment detectors.
Posted Date:2010-07-02 08:41:15.0
Hello, Im relatively new to the (vast) world of experimental optics. Ive greatly enjoyed browsing your catalog...particularly the application ideas with various products. I recently was looking at your 4 quadrant photo diode position detectors PDQ80A and PDP90A. In the application idea, you have an application idea for an auto-alignment setup. Its not clear to me, however, what experimental problem this application is trying to solve. Perhaps a sentence or two in the description would greatly help us newbies. Thus, as we encounter problems, we can look at your applications and discover exactly how the pros solve the problem that we may experience. In the application, why would the laser beam move around? What advantage does the setup give that makes it supierior to locking down the laser on the table? Thermal drift? Mechanical Vibrations? Laser variability? Thanks, Geoff
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PDP90A Support Documentation
PDP90A2D Lateral Effect Position Sensor, 320 to 1100 nm

Quadrant Position Detectors

Item #PDQ80APDQ30C
Substrate Si InGaAs
Wavelength Range 400 - 1050 nm 1000 - 1700 nm
Detector Bandwidth 150 kHz 150 kHz
Recommended Spot Size Ø1.0 - 3.9 mm Ø0.2 - 0.5 mm
Click Image to Zoom


  • Segmented Quadrant Position-Sensing Detector
  • Versions for Visible or NIR
  • Ideal for Automatic Alignment
  • Compatible with Four Channel Position Sensing System or a Single Channel T-Cube
  • SM05 Lens Tube Compatible
  • Compact Footprint

Thorlabs' offers a wide variety of coherent light sources compatible with both quadrant detectors. A selection of appropriate lasers is outlined on the Suggested Lasers tab. Sample position sensing arrangements are shown in the Application Idea tab. For questions about specific light detection arrangements contact tech support.

The PDQ80A and PDQ30C detectors are segmented, position-sensing, quadrant detectors for precise path alignment of light in the 400 to 1050 nm or 1000 to 1700 nm range, respectively. A 6-pin Hirose connector on each detector outputs signals proportional to the incident beam's power distribution (and thus position). For best results, quadrant detectors should be used with powers under 1 mW (linear regime of sensor) and beam diameters within their specified range.

Each quadrant detector is packaged with an 8-32 to M4 adapter to provide compatibility with either imperial or metric mounting posts. A controller, TPA101, is available separately below.

Item #PDQ80APDQ30C
Wavelength Range400 - 1050 nm1000 - 1700 nm
Photodiode DiameterØ7.8 mmØ3.0 mm
Gap Size42 μm45 µm
Detector Bandwidth150 kHz150 kHz
Responsivity0.45 A/W @ 633 nm1 A/W @ 1630 nm
Transimpedance Gain10 kV/A
Dark Current
(V Rvrs = 10 V)
5 nA2.0 nA Typ,
100 nA Max
Rise Time, Typical40 ns @ 10 V24 ns @ 5 V
Breakdown Voltage15 V10 V
Damage Threshold100 mW/cm2100 mW/cm2
Housing Dimensions2.0" x 1.20" x 0.65"
Cable Length5 ft (1.52 m)
Mounting Threads8-32 (with M4 Adapter Included)

6 pin Hirose Connector

6-Pin Hirose Connector

Pin #Assignment
4+V (5 to 15 V)
6-V (-5 to -15 V)

Segmented-Quadrant Position-Sensing Detectors

Seqmented-Quadrant PSD

The segmented-quadrant position sensors consists of four distinct yet identical quadrant-shaped photodiodes that are separated by a ~0.1 mm gap and together form a circular detection area capable of providing a 2D measurement of the position of an incident beam. When light is incident on the sensor, a photocurrent is detected by each sector (labeled Q1, Q2, Q3, and Q4 as shown in the figure to the right). From these signals difference signals can be determined using an appropriate A/D converter. The sum of all four signals is also determined for normalization purposes. The normalized coordinates (X, Y) for the beam's location are given by the following equations.

X Position Equation

Y Position Equation

If a symmetrical beam is centered on the sensor, four equal photocurrents will be detected, resulting in null difference signals, and hence, the normalized coordinates will be (X, Y) = (0, 0). The photocurrents will change if the beam moves off center, thereby giving rise to difference signals that are directly proportional to the beam displacement from the center of the sensor.

These sensors are very accurate and are ideal for auto-alignment applications. However, care should be taken in the shape and density distribution of the incident beam. These sensors are sensitive to these two parameters. A beam that does not have a Gaussian power distribution will be centered based on the power, rather than the geometric center of the beam. For these types of beams, a lateral sensor might be better suited.

Detector Out - HIROSE

HiRose Out

Photodiode Detail

Photodiode Detail

1X-axis [Q2 +Q3] - [Q1 + Q4]
2Y-axis [Q1+Q2] - [Q3 + Q4]
3SUM [Q1 +Q2 + Q3 + Q4]
4+5 V to +15 V
6-5 V to - 15 V

TPA101 Auto-Aligner and PDQ80A Photodiode Sensor in an Auto-Alignment Setup

A basic auto-alignment schematic is shown below. It consists of a PDQ80A Photodiode Sensor, a TPA101 PSD Auto-Aligner, two TPZ001 piezo drivers, a piezo-actuated 2-axis turning mirror mount (Item # ASM003), a laser source, and a computer. Together, the system is used to position and maintain the laser beam so that it is located at the center of the detector array with respect to power density.

It should be noted that when used with older versions of the TPZ001 T-Cubes (i.e., Rev. 1. The revision number is displayed on the LED screen when the T-Cube is booted), the piezo cubes must be connected to the TPA101 Auto-Aligner using two external SMA connectors even if a TCH002 hub is being used; if Rev. 2 or higher TPZ001 T-Cubes are used with a TCH002 hub, the SMA to SMA cables are not needed. However, regardless of revision number, SMA to SMA cables are needed if the TCH002 hub is not used.

Application Schematic

Typical Auto-Alignment Setup

TQD001 Experimental Setup

Thermal variations in a lab cause misalignment of components. Optical tables are susceptible to bowing dependent on the different coefficients of thermal expansion of top and bottom plates. Mechanics such as mirror mounts exhibit drift from temperature variation. By using a quadrant detector in a closed-loop system, one can minimize the effects of thermal variation on an experiment's alignment.

The experimental setup shown to the right was created based on the schematic above. An LDM635 red laser diode module outputting light at 635 nm serves as the laser source. The light is incident on an ASM003 turning mirror mount, which is mounted on a MBT616 flexure stage (center of photo). The turning mirror's x and y motions are controlled using two TPZ001 piezo actuators (these are the first and third T-Cubes shown on the TCH002 hub at the bottom of the picture). Please note that the piezo elements are meant for small beam alignment adjustments. The turning mirror directs light to a BP150 pellicle beamsplitter. The light transmitted by this beamsplitter will continue on to the rest of the experimental setup (not shown) while the reflected light is directed towards the PDQ80A Quadrant Sensor (back right of photo), which is controlled by the TPA101 Auto-Aligner (located next to the TPZ001 piezo drivers on the TCH002 hub).

When using a Quadrant Detector, choosing an appropriate alignment laser is essential. The laser's wavelength, beam diameter, and power all have a significant effect on the performance of the system. While there are countless sources that are suitable for use with our quadrant detectors, the lasers and optical components below have been selected for their cost-effectiveness and ease of use.

Photodiodes, such as those used in our quadrant detectors, should have less than 1 mW of incident light on them for linear responsivity. Beam splitters are commonly used in auto-alignment systems and reduce the amount of light on the detector. Depending on the optical setup, the laser's power may need to be further reduced, which can be accomplished using the power adjustment knob on our T-Cube lasers.

The suggested fiber patch cables are each 2 m long and are matched to the fiber type in the laser source. While we offer many different collimators, the ones suggested here are part of our Adjustable Collimator line and provide an appropriately-sized beam diameter for use with our Quadrant Detectors. The collimators can be mounted numerous ways, but the VC1 (VC1/M) is a versatile solution suitable for most applications.

PDQ80A Compatible

  • Wavelength Range: 400 - 1050 nm
  • Input Beam Diameter: 1 - 3.9 mm
  • Max Incident Power (for Linear Response): 1 mW
LaserLaser DescriptionPower SupplyFiber (2 m Length)Collimator
TLS001-635635 nm, 2.5 mW Fiber-Coupled T-Cube LaserTPS101P1-630A-FC-2CFC-11X-A

PDQ30C Compatible

  • Wavelength Range: 1000 - 1700 nm
  • Input Beam Diameter: 0.2 - 0.5 mm
  • Max Incident Power (for Linear Response): 1 mW
LaserDescriptionPower SupplyFiber (2 m Length)Collimator
TLS001-15501550 nm, 1.5 mW Fiber-Coupled T-Cube LaserTPS101P1-SMF28E-FC-2CFC-2X-C
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Click the Support Documentation icon document icon or Part Number below to view the available support documentation
Part NumberProduct Description
PDQ30C Support Documentation PDQ30C:Quadrant Detector Sensor Head, 1000 to 1700 nm
PDQ80A Support Documentation PDQ80A:Quadrant Detector Sensor Head, 400 to 1050 nm

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Posted Comments:
Posted Date:2011-01-11 10:55:21.0
A response from Greg at Thorlabs to infante.cristian: Based on your feedback, I have added the Hirose pin diagram to the Specs tab. We will contact you to discuss centroid detection.
Posted Date:2010-12-31 01:32:27.0
Im very interested on using PDQ80A to detect the beam centroid. Q1: What signals are available in the outputs (6-pin Hirose)?. Please mail me to discuss this and other products for centroid detection. Thanks!
Posted Date:2010-08-11 16:15:42.0
To handle less intensive light sources, is it possible to increase the gain of the PDQ80A?
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PDQ80A Support Documentation
PDQ80AQuadrant Detector Sensor Head, 400 to 1050 nm
PDQ30C Support Documentation
PDQ30CQuadrant Detector Sensor Head, 1000 to 1700 nm

T-Cube Position Sensing Detector (PSD) Controller

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Item #TPA101
X & Y Difference / Position
Demand Outputs
-10 to 10 V, SMA Connectors
Sum Output 0 to 10 V, SMA Connector
Quadrant Detector Input 6-Pin HRS Connectora
Closed-Loop Bandwidth Up to 1 kHzb
Open-Loop Bandwidth (-3.0 dB) 100 kHz
Dimensions (W x D x H) 60 mm x 60 mm x 47 mm
(2.4" x 2.4" x 1.8")
Weight 160 g (5.5 oz)
  • See Pin Diagrams tab for details.
  • When driving TPZ001 Piezo Controllers at 10% FSD (Full Scale Deflection), the bandwidth is 200 Hz.

Click to Enlarge

The image above shows a top view of the TPA101 T-Cube.


  • Auto Alignment of Beam to Center of Sensor when in Closed-Loop Mode
  • Beam Position Measurement when in Open-Loop Mode
  • LED Crosshair Position Display
  • USB and Manual Control Interfaces
  • Voltage Outputs for Sum, Difference, and Feedback Signals
  • Flexible Software Suite (See APT Software Tab)
  • Compact T-Cube Footprint: 60 mm x 60 mm x 47 mm (2.4" x 2.4" x 1.8")
  • Compatible with T-Cube Hub System

The TPA101 T-Cube Beam Position Aligner interfaces with our range of Quadrant and Lateral Effect Sensor Heads and can be used either to measure the position of the beam on the sensor (in Open Loop mode) or to generate a signal that can be used as the feedback input for an automated beam steering element (in Closed Loop mode).

When operating in Closed Loop mode, the proportional, integral, and differential (PID) constants can be adjusted to fine tune the response of the feedback loop to changes in the target position. The TPA101 uses floating-point arithmetic that allows a greater range of PID coefficients to be used in the control loop, resulting in higher precision and lower noise (see Appendix B of the manual for details). This increases the range of actuators that can be stabilized using the controller. Furthermore, the unit incorporates a notch filter that can be used to counteract the natural resonance of the specific mechanical system in which the unit is being used, and can stabilize actuators that are prone to mechanical resonances, such as piezo mirror gimbal mounts.

The output signal generated can be used to steer the center of the beam's power density to the center of the sensor head. When combined with the TPZ001 Piezo Driver T-Cubes, this unit is ideal for such closed-loop beam-steering applications. Please contact tech support for details on how the TPA101 can be used with sensors from other manufacturers.

The TPA101 T-Cube can be controlled by the manual interface on the top of the unit or via a USB connection to a computer running the included apt™ software (see APT Software tab) or ActiveX command modules. Both interfaces allow the TPA101 to be operated in either an open- or closed-loop mode. The open-loop mode is used to measure the position of the beam on the detector. When in this mode, the T-Cube generates a left-minus-right X difference signal, a bottom-minus-top Y difference signal, and a sum signal.

In the closed-loop mode, a DSP processor inside the TPA101 runs two independent feedback loops that generate X and Y position demand outputs for use as the input to the beam steering element being used to center the beam on the detector. The beam position information (open-loop mode) or feedback signals (closed-loop mode) are available via SMA connectors on the side of the unit. When the unit is controlled via the USB interface, the open-loop output of the unit is also exported digitally to the computer.

Power Supply Options
The TPA101 T-Cube, which does not ship with a power supply, can be powered using either a TPS002 power supply or a TCH002 T-Cube Hub and Power Supply. The TPS002 power supply plugs into a standard wall outlet and provides +15 VDC, -15 VDC, and +5 VDC for up to two T-Cubes. In contrast, the TCH002 consists of two parts: a hub that can support up to six standard footprint T-Cubes and a power supply that plugs into a standard wall outlet and powers the hub, which in turn powers all of the T-Cubes connected to the hub.

The hub's single USB connection provides USB connectivity to all the T-Cubes plugged into the hub. In addition, when the TPA101 is used in the closed-loop mode with beam-steering controllers such as the TPZ001 Piezo Driver T-Cubes, the hub is especially useful since it allows for direct communication between the T-Cubes connected on it. As a result, the feedback signals generated by the TPA101 in the closed-loop mode can be sent directly to the TPZ001 piezo controllers being used to direct the beam steering elements.

For more details on the TPA101 T-Cube, please see its full web presentation.

Detector In - HIROSE HR10A-7R-6S

Detector In

Photodiode Detail

Photodiode Detail

1 X-Axis [Q2 + Q3] - [Q1 + Q4] (-10 to +10 V)
2 Y-Axis [Q1 + Q2] - [Q3 + Q4] (-10 to +10 V)
3 SUM [Q1 + Q2 + Q3 + Q4] (0 to +10 V)
4 +V (+15 V, 15 mA Max)
5 Common
6 -V (-15 V, 15 mA Max)


SMA Female


3 connectors output signals proportional to the total amount of light hitting the detector (SUM), left-minus-right (LV OUT XDIFF), & top-minus-bottom (LV OUT YDIFF) for X- and Y-axis alignment.

Computer Connection

USB Mini-B*

USB Mini-B

* 2 m (6.6') USB type Mini-B to type A cable included.


Version 3.5.0

Includes a GUI for control of Thorlabs' APT™ system controllers, as well as a wealth of support information in the form of handbooks, help files, tutorial videos, and FAQs.

Also Available:

  • Support Package
  • Redistribution Module
Software Download

The APT™ (Advanced Positioning Technology) family covers a wide range of motion controllers ranging from small, low-powered, single-channel drivers (such as the T-Cubes) to high-power, multi-channel, modular 19" rack nanopositioning systems (the APT Rack System).

All controllers in the APT family share a common software platform, the 'APT System Software', which is available on our APT software download page. A support package, containing a wealth of information on using and programming these Thorlabs products is also available.

By providing this common software platform, Thorlabs has ensured that users can easily mix and match any of the APT controllers in a single application, while only having to learn a single set of software tools. In this way, it is perfectly feasible to combine any of the controllers from the low-powered, single-axis to the high-powered, multi-axis systems and control all from a single, PC-based unified software interface.

The APT System Software allows two methods of usage: graphical user interface (GUI) utilities for direct interaction and control of the controllers 'out of the box', and a set of programming interfaces that allow custom-integrated positioning and alignment solutions to be easily programmed in the development language of choice.

A range of video tutorials are available to help explain our APT system software. These tutorials provide an overview of the software and the APT Config utility. Additionally, a tutorial video is available to explain how to select simulator mode within the software, which allows the user to experiment with the software without a controller connected. Please select the APT Tutorials tab above to view these videos, which are also available on the software cd included with the controllers.

Typical APT User GUI
Typical Configuration Screen
Click the Support Documentation icon document icon or Part Number below to view the available support documentation
Part NumberProduct Description
TCH002 Support Documentation TCH002:T-Cube Controller Hub and Power Supply Unit
TPA101 Support Documentation TPA101:T-Cube PSD Auto Aligner (Power Supply Not Included)
TPS002 Support Documentation TPS002:±15 V/5 V Power Supply Unit for up to 2 T-Cubes

Please Give Us Your Feedback
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Enter Comments Below:
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Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
TPA101 Support Documentation
TPA101Customer Inspired!T-Cube PSD Auto Aligner (Power Supply Not Included)
TPS002 Support Documentation
TPS002±15 V/5 V Power Supply Unit for up to 2 T-Cubes
TCH002 Support Documentation
TCH002 T-Cube Controller Hub and Power Supply Unit
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