Optical Sensors - Photodiodes

Part Number	Description / PDF	Quantity
LTR-323DB Lite-On, Inc.	SENSOR PHOTODIODE 900NM RADIAL	0
HSDL-5400#031 Lite-On, Inc.	SENSOR PHOTODIODE 875NM 2SMD	0
LTR-516AD Lite-On, Inc.	SENSOR PHOTODIODE 940NM RADIAL	907
HSDL-5420#011 Lite-On, Inc.	SENSOR PHOTODIODE 875NM 2SMD GW	6
HSDL-5400#011 Lite-On, Inc.	SENSOR PHOTODIODE 875NM 2SMD GW	0
LTR-516AB Lite-On, Inc.	SENSOR PHOTODIODE 900NM RADIAL	0
LTR-546AD Lite-On, Inc.	SENSOR PHOTODIODE 900NM RADIAL	0
HSDL-5420 Lite-On, Inc.	SENSOR PHOTODIODE 875NM 2SMD	2075
LTR-536AB Lite-On, Inc.	SENSOR PHOTODIODE 900NM RADIAL	0
HSDL-5400 Lite-On, Inc.	SENSOR PHOTODIODE 875NM 2SMD	0
HSDL-5420#031 Lite-On, Inc.	SENSOR PHOTODIODE 875NM 2SMD	12389
LTR-536AD Lite-On, Inc.	SENSOR PHOTODIODE 900NM RADIAL	0
LTR-743DBM1-TA Lite-On, Inc.	SENSOR PHOTODIODE 880NM RADIAL	0
LTR-526AD Lite-On, Inc.	SENSOR PHOTODIODE 900NM RADIAL	0
HSDL-5420#021 Lite-On, Inc.	SENSOR PHOTODIODE 875NM 2SMD	0
HSDL-5420#1L1 Lite-On, Inc.	SENSOR PHOTODIODE 875NM 2SMD	0
HSDL-5400#1L1 Lite-On, Inc.	SENSOR PHOTODIODE 875NM 2DIP	0
LTR-546AB Lite-On, Inc.	SENSOR PHOTODIODE 900NM RADIAL	0
LTR-526AB Lite-On, Inc.	SENSOR PHOTODIODE 900NM RADIAL	0

Optical Sensors - Photodiodes

1. Overview

Photodiodes are semiconductor devices that convert optical signals into electrical currents. Operating under reverse bias voltage, they generate electron-hole pairs when exposed to light, enabling precise light intensity measurement. As critical components in optoelectronics, photodiodes enable applications ranging from industrial automation to medical diagnostics, offering advantages like fast response times, high reliability, and compatibility with digital systems.

2. Major Types and Functional Classification

Type	Functional Characteristics	Application Examples
PIN Photodiode	Wide depletion region for high quantum efficiency	High-speed optical communication (e.g., 10Gbps fiber links)
Avalanche Photodiode (APD)	Internal gain through impact ionization	LIDAR systems, single-photon detection
Schottky Photodiode	Low capacitance for fast switching	UV radiation monitoring in semiconductor manufacturing
Metal-Semiconductor-Metal (MSM)	Planar structure for high-frequency operation	Optical interconnects in data centers
UV Photodiode	Spectral sensitivity below 400nm	Flame detection systems, water purification monitoring

3. Structure and Components

Photodiodes typically consist of a p-n junction or p-i-n structure fabricated from silicon, germanium, or indium gallium arsenide (InGaAs). The core components include: (1) Light-receiving window with anti-reflective coating, (2) Active semiconductor layer for photon absorption, (3) Electrodes (anode/cathode) for current collection, (4) Ceramic or plastic package with optical filter integration. Advanced designs incorporate micro-lenses and back-illuminated structures to enhance quantum efficiency.

4. Key Technical Specifications

Parameter	Description	Importance
Responsivity (A/W)	Current output per unit optical power	Determines signal strength at given irradiance
Dark Current (nA)	Leakage current without illumination	Impacts signal-to-noise ratio in low-light conditions
Rise Time (ns)	Response speed to intensity changes	Critical for high-frequency modulation applications
Junction Capacitance (pF)	Parasitic capacitance at depletion region	Limits bandwidth in transimpedance amplifier circuits
Spectral Response Range (nm)	Effective wavelength detection window	Dictates compatibility with light sources (e.g., 850nm VCSELs)

5. Application Fields

Industrial Automation: Object detection in conveyor systems
Medical Imaging: X-ray detectors in CT scanners
Consumer Electronics: Proximity sensors in smartphones
Telecommunications: 100Gbps coherent optical receivers
Environmental Monitoring: Solar radiation sensors for weather stations

6. Leading Manufacturers and Products

Manufacturer	Representative Product	Key Features
Hamamatsu Photonics	S1223-6BQ	High-speed Si photodiode with 1.3GHz bandwidth
OSRAM Opto	BFW21R	Blue-enhanced PIN diode for LiDAR applications
First Sensor	FDS030	Low-noise APD for single-photon counting
Excelitas Technologies	C30655GH	InGaAs photodiode for 1.55 m telecom wavelengths
Vishay Semiconductors	BPW34S	High-radiation hardness for industrial sensors

7. Selection Recommendations

Key considerations include: (1) Spectral matching with light source (e.g., InGaAs for 1550nm fiber systems), (2) Response time requirements (PIN vs APD tradeoffs), (3) Operating temperature range (-40 C to +85 C industrial grade), (4) Packaging constraints (SMD vs through-hole), and (5) Cost vs performance optimization (e.g., APDs require bias voltage regulators).

Industry Trends

Current development focuses on: (1) Graphene-based photodiodes for THz imaging, (2) CMOS-integrated single-photon avalanche diodes (SPADs) for LiDAR, (3) Flexible organic photodiodes for wearable devices, (4) Quantum dot photodiodes for extended IR sensitivity, and (5) AI-driven smart sensors with on-chip signal processing. Market growth is projected at 7.2% CAGR through 2028, driven by 5G optical networks and autonomous vehicle sensing systems.