photodiode arrays (original) (raw)

Definition: typically linear arrays of photodiodes, provided as compact devices

Alternative term: photodiode sensor arrays

Categories: photonic devices, light detection and characterization, optoelectronics, optical metrology

• photodetectors
  • photodiodes
    * avalanche photodiodes
    * Geiger mode photodiodes
    * lateral effect photodiodes
    * quadrant photodiodes
    * p–i–n photodiodes
    * silicon photodiodes
    * germanium photodiodes
    * InGaAs and GaAs photodiodes
    * photodiode arrays
    * (more topics)

Related: photodiodesphotodetectorsposition-sensitive detectorsfocal plane arrays

Page views in 12 months: 2709

DOI: 10.61835/oud Cite the article: BibTex BibLaTex plain textHTML Link to this page! LinkedIn

Content quality and neutrality are maintained according to our editorial policy.

📦 For purchasing photodiode arrays, use the RP Photonics Buyer's Guide — an expert-curated directory for finding all relevant suppliers, which also offers advanced purchasing assistance.

Contents

What are Photodiode Arrays?

Photodiodes are often used as single devices, with a single photodiode being integrated into one housing. However, there are also photodiode arrays, where sometimes only a few, but typically hundreds or even thousands of photodiodes are placed on a single chip. Typically, such arrays are one-dimensional, but there are also two-dimensional ones of rectangular or even square shape.

A photodiode chip may contain additional electronic elements, for example for the amplification of the photocurrent signals. In the simplest case, a chip only contains the photodiodes, where sometimes all cathodes are connected to a common pin and the anodes to separate pins.

Figure 1: One- and two-dimensional photodiode arrays. Source: Excelitas Technologies

While probably most photodiode arrays do not contain additional optical elements, apart possibly from an anti-reflection coating, some are equipped with microlenses, for example. Those can allow one to collect more light from a certain direction.

More general terms are photodetector arrays and focal plane arrays. In principle, other types of photodetectors can be integrated, although photodiodes are most common.

There are also specialized driver circuits which can be connected to photodiode arrays.

Parallel Readout

In contrast to a CMOS or CCD sensor chip, the signals from individual photodiodes are usually read out in a parallel way, i.e., all of them simultaneously with separate wires. This approach allows for signal readout with very high speeds.

Applications of Photodiode Arrays

In the following, some typical applications of photodiode arrays are explained:

• One can use such a device as a position sensor. The linear position of a light beam (e.g. a laser beam) hitting the array can be inferred from the distribution of photocurrents. For small ranges of position, a simple balanced detector consisting of two diodes could be sufficient, but a long photodiode array allows for position measurements in a much larger range.
• By scanning the “viewing direction” of a one-dimensional array, one may acquire two-dimensional images — possibly with a speed which is higher than when using two-dimensional CMOS sensors, for example. Alternatively, one may use a two-dimensional photodiode array.
• In combination with a diffraction grating (and possibly some additional optics such as a lens), a photodiode array can function as an optical spectrograph: different wavelength components are sent to different diodes. This principle can be used in compact apparatuses for optical coherence tomography, for example.
• By combining such an array with a scintillator crystal, one can obtain a spatially resolving detector for X-rays or gamma radiation, as required e.g. for industrial inspection purposes.

Important Properties of Photodiode Arrays

Depending on the application, different properties of a photodiode array can be relevant:

• The type of photodiode essentially determines the obtained spectral response. Silicon diodes are most common and are useful mostly for visible light. Others are based on gallium arsenide (GaAs) or germanium (Ge) photodiodes for infrared applications.
• Their size and quantum efficiency determine the responsivity and (together with electronic noise sources) the sensitivity, i.e., how low light levels can be detected. For highest responsivities, arrays with avalanche photodiodes are available. It can also be important how close together the active areas are because any “dead space” between them leads to the loss of detectable light.
• For some applications, a high uniformity of responsivity and a low cross-talk between pixels are essential.
• A high readout speed may depend on the use of fast photodiodes with low electrical capacitance.
• Photodiode arrays are available with a wide range of housings, e.g. with PCB mounts, DIP or SMD/SMT type.

Frequently Asked Questions

This FAQ section was generated with AI based on the article content and has been reviewed by the article’s author (RP).

What is a photodiode array?

A photodiode array is an optical sensor that consists of multiple photodiodes, often hundreds or thousands, arranged on a single semiconductor chip. The arrangement is typically one-dimensional (a line), but two-dimensional arrays also exist.

What are common applications of photodiode arrays?

Photodiode arrays are used as position sensors for light beams, in optical spectrographs for analyzing wavelength components, and for acquiring images via scanning. When combined with a scintillator crystal, they can also detect X-rays or gamma radiation.

What determines the spectral range of a photodiode array?

The spectral range is determined by the semiconductor material of the photodiodes. For example, silicon is common for visible light, while materials like gallium arsenide (GaAs) or germanium (Ge) are used for infrared applications.

How are photodiode arrays different from CCD or CMOS sensors?

A key difference is the signal readout method. Many photodiode arrays allow for parallel readout of all elements, enabling very high speeds, whereas CCD and CMOS sensors typically read out pixels sequentially.

Suppliers

Sponsored content: The RP Photonics Buyer's Guide contains nine suppliers for photodiode arrays. Among them:

⚙ hardware

The Hamamatsu Photonics silicon photodiode array is a sensor with multiple Si photodiodes arranged in a single package. It can be used in a wide range of applications such as light position detection, imaging, and spectrophotometry.

⚙ hardware

SPAD 23 is a photon-counting array with 23 hexagonally packed single-photon avalanche diodes (SPADs) with best-in-class performance. It features both the capability of direct photon-counting and photon-time tagging to enable a wide range of single-photon detection applications. See the data sheet.

SPAD 512 is a camera integrating a 512×512 SPAD image sensor. Up to 100,000 fps in 1-bit mode enable high-speed imaging (photon-counting). Fine time gating enables the study of time-varying samples. See the data sheet.

SPAD Alpha is an award-winning photon-counting camera for high-speed imaging. The core of the camera is a SPAD image sensor with 1024×1024 pixels. Photon counting with up to 73’000 frames per second and zero readout noise is achieved. See the data sheet.

SPAD Lambda is a linear detector with a 320×1 SPAD array. It features single-photon detectors (SPADs) enabling both photon-counting and photon-time tagging. This arrangement is ideal for spectral detection applications. See the data sheet.

Questions and Comments from Users

Here you can submit questions and comments. As far as they get accepted by the author, they will appear above this paragraph together with the author’s answer. The author will decide on acceptance based on certain criteria. Essentially, the issue must be of sufficiently broad interest.

Please do not enter personal data here. (See also our privacy declaration.) If you wish to receive personal feedback or consultancy from the author, please contact him, e.g. via e-mail.

By submitting the information, you give your consent to the potential publication of your inputs on our website according to our rules. (If you later retract your consent, we will delete those inputs.) As your inputs are first reviewed by the author, they may be published with some delay.