Photodiode

Tech-LED’s Photodiode category encompasses a range of semiconductor light detectors, including PN and PIN photodiodes, optimized for different spectral ranges from UV through visible to IR. Photodiodes are the complementary devices to LEDs – where LEDs emit light, photodiodes absorb light and generate an electrical current proportional to intensity. We offer photodiodes in various package types (hermetic TO cans, plastic packages, surface-mount, etc.) and in different junction types to cater to specific needs: silicon photodiodes for UV-visible-NIR (roughly 200–1100 nm sensitivity), InGaAs photodiodes for NIR-SWIR (800–1700 nm), and specialty two-junction photodiodes that cover broad ranges (like our two-tone photodiode combining Si and InGaAs in one package for 400–1700 nm coverage). These photodetectors are used in sensor systems to convert optical signals to electrical signals for measurement or control. Tech-LED photodiodes are designed for high sensitivity, low noise, and fast response, aligning with applications such as ambient light sensing, optical communication receivers, safety sensors, medical instrumentation, and spectroscopy.

Notable Features of Tech-LED Photodiodes

Broad Spectral Coverage Options

We provide photodiodes tailored to different parts of the spectrum. Our silicon photodiodes excel in the visible and near-IR (peak typically around 900 nm, with response from ~200 nm with UV-enhancement to about 1100 nm). We have UV-enhanced Si photodiodes with special window materials or surface treatments to detect down to 220–300 nm for flame detectors or UV monitors. For deeper IR, our InGaAs photodiodes cover roughly 800–1700 nm (standard) or even extended InGaAs that can go to 2000 nm. These are ideal for telecom (1300/1550 nm) and SWIR sensing (like the 1450 nm water absorption line). We also produce dual-band photodiodes like the two-tone photodiode KPMC29 which integrates a silicon diode and an InGaAs diode aligned optically. This device has a continuous sensitivity from 400 nm to 1700 nm in one package, which is excellent for broad-spectrum radiometers or any sensor that needs to mimic the eye plus beyond. Offering these choices means designers can pick a photodiode that perfectly matches the emission of their source or the spectral signature they need to detect, improving system SNR and efficiency.

High Speed and Low Capacitance

Many of our photodiodes are PIN structure, which lowers junction capacitance and enables fast response times in the nanosecond to microsecond range, depending on biasing and area. For example, our small-area Si PIN photodiodes can have rise times of a few nanoseconds, making them suitable for high-speed optical communication or LiDAR receivers. We specify bandwidths for our photodiodes used in fiber optics, e.g., a 2 mm² InGaAs photodiode might have a capacitance of tens of pF and can be used up to tens of MHz easily, whereas a smaller 0.3 mm InGaAs can go into the GHz range for telecom receivers. Similarly, for visible light communications or fast optical sensors (like laser rangefinders), we have photodiodes packaged in RF-friendly mounts (e.g., coaxial or with short leads) to preserve bandwidth. Low capacitance also equates to low noise when photodiodes are used in high impedance circuits, improving sensitivity in low-light conditions. Our designs often come in hermetic RF packages (like TO-46 with a coaxial connector) for the highest speed applications, ensuring minimal signal distortion.

Large Area & Sensitive Photodiodes

For applications like ambient light sensing, solar measurement, or presence detection, having a large active area is beneficial to collect more light. We offer photodiodes with active areas ranging from a few square millimeters up to even ~1 cm² (in photodiode arrays or large active area detectors). For example, our 5 mm × 5 mm Si photodiode in a daylight filter window is often used as an ambient light sensor in outdoor controls – large area ensures good representative sampling of light and easier matching of human eye response when combined with an appropriate filter. We also have photodiode arrays (like 4-element quadrant photodiodes for position sensing or beam alignment). The large area devices operate typically at lower bandwidth but maximize signal in low-light conditions – crucial for scientific instruments measuring very weak signals. We often integrate optical filters either as coatings or glass windows to shape the spectral response, ensuring application-specific accuracy (for example, a lux sensor photodiode with a built-in IR-cut filter to mimic the human eye).

Low Dark Current and High Dynamic Range

In sensor applications, the quality of a photodiode is partly measured by how low its dark current (leakage in absence of light) is and how well it can handle a wide range of light intensities. Tech-LED photodiodes are manufactured with high-purity materials and optimized processes to minimize dark current. Our Si photodiodes typically have dark currents in the nA range or lower at room temperature (depending on area), and InGaAs photodiodes similarly controlled. This low dark current equates to a lower noise floor in detection circuits, enabling detection of weaker signals. Additionally, our photodiodes can often be used both in photovoltaic (no bias) mode for simplicity in moderate light, and photoconductive (reverse biased) mode for faster response or low-light amplification. They are linear over many decades of light intensity, providing reliable output from near dark up to saturation. For designs like optical power meters, linearity and stable responsivity across intensities and over time are crucial – we calibrate and provide data for our photodiodes that go into calibrated measurement gear.

Integration into Emitters and Modules

While photodiodes are components in their own right, Tech-LED also integrates them into modules or with emitters for convenience. A typical example is an optical interrupter module: a U-shaped housing with an IR LED on one arm and a photodiode on the other. Similarly, our photodiode receivers may come with built-in pre-amplifiers in some modules (like a remote control IR receiver module). Our two-tone photodiode (Si+InGaAs) is an example of integration at the chip level for broader use, targeted at spectral sensing without needing two separate detectors and alignment. This integration capability means we can deliver custom photodiode arrays or combinations that reduce assembly complexity for the end user – for example, packaging a UV photodiode and an IR photodiode with a beam-splitter filter in one can, acting as a compact dual-sensor.

Applications of Photodiodes

Ambient Light and Proximity Sensors (Consumer Devices)

Photodiodes are ubiquitous in phones, laptops, and IoT devices as ambient light sensors (to adjust screen brightness) and in proximity sensors (like the one that turns off your phone screen when you hold it to your ear). Tech-LED supplies tiny SMD photodiodes with spectral filtering to closely mimic human eye response for ambient light. For proximity, typically an IR photodiode detects reflection from an IR LED – we ensure our photodiodes in those modules have fast response and daylight filtering (so they ignore sunlight and respond only to the 850–940 nm from the IR LED). Our photodiodes’ low capacitance and optimized packaging contribute to the rapid toggling needed in these cases (often they measure pulsed IR up to 100–200 kHz).

Fiber Optic and Optical Communication Receivers

Photodiodes (especially InGaAs PIN photodiodes) are the workhorse detectors in fiber optic communication – from long-haul telecom to short-range optical interconnects. Tech-LED’s InGaAs photodiodes are used in receivers for 1310 nm and 1550 nm fiber links, including high-speed photodiodes in TO-46 packages for telecom data rates. We also supply larger InGaAs photodiodes for receivers in free-space optical communication systems where sensitivity is key. In visible light communications (Li-Fi) or IR communication (like IrDA in older devices), our silicon photodiodes often served as the detection element. A concrete example: the Infrared Data Association (IrDA) standard modules often used a Si PIN photodiode in a small can as the IR receiver – our photodiodes met the rise time requirements and were integrated with a transimpedance amp in one package. In new Li-Fi trials, high-speed silicon photodiodes we produce (with bandwidths ~20–50 MHz) are used to receive modulated light from LEDs for wireless data within rooms.

Industrial and Safety Sensors

Photodiodes are key in many industrial sensors – from beam break sensors on assembly lines to flame detectors (UV photodiode senses UV emissions from flames, triggering alarms). Our UV-enhanced Si photodiodes are installed in flame detection systems in oil rigs and kitchens. Another safety use is smoke detection, which uses IR photodiodes – we provide those as well, tuned to the expected scattering wavelengths. Additionally, radiation monitoring uses photodiodes: scintillator crystals emit light when exposed to radiation, and photodiodes read that light. We provide large area photodiodes optically coupled to scintillators for portable radiation detectors. In optical encoders and optical switches, photodiodes convert light pulses to digital signals to measure speed or presence. For example, an elevator door safety uses an array of photodiodes across the doorway receiving IR beams; if any beam is broken, it signals the door to reopen.

Medical Devices (Pulse Oximetry, Spectroscopy)

In pulse oximeters (both fingertip clips and wearables), a photodiode detects transmitted or reflected red and IR light through tissue. Tech-LED’s photodiodes for this have high sensitivity and are packaged with daylight filters to avoid ambient interference. Our two-tone photodiode concept also finds interest in advanced oximetry where measuring a broader spectrum could allow extraction of more blood parameters. In diagnostic machines, photodiodes read signals from chemical assays – e.g., a UV LED excites fluorescence in a sample and a photodiode measures it. In NIR spectroscopy devices for tissue analysis, InGaAs photodiodes measure absorption at various wavelengths; their stable response and low dark current at body temperature are crucial for reliable readings.

Laser Detection and LiDAR

Photodiodes detect laser returns in LiDAR systems (unless APDs or SPADs are used for very long ranges). For many moderate-range LiDAR (like automotive up to 100 m), an array of PIN photodiodes can suffice. Tech-LED provides photodiodes used in some solid-state LiDAR designs at 905 nm or 940 nm. Their fast response and the ability to form arrays help create scanning or flash LiDARs. In laser rangefinders (for surveying or drone altimeters), typically a photodiode in a can with a fast amplifier catches the reflected laser pulse. Also, in laser power meters and laser safety sensors, photodiodes measure continuous laser output to ensure it’s within desired levels or to cut off if too high. We provide calibrated photodiodes for laser power monitoring integrated into laser systems.

In sum, Tech-LED’s photodiodes serve as the “eyes” in countless systems, from everyday consumer electronics to sophisticated industrial and scientific apparatus. With our wide spectral offerings, high performance design, and capacity to customize, we ensure that if there’s light to be measured – be it UV, visible, or IR – our photodiodes can measure it with precision and reliability, complementing our LED emitters to provide full optical solutions.