Red and Infrared Laser Diode & Infrared LED FAQ

What is the difference between laser diodes (LD) and light emitting diodes (LEDs)?

Are there any cautions for handling laser diodes?

What are the applications of the infrared LED (IRED)?

Which safety standard do Opnext laser diodes comply with?

What laser diode line up does Opnext have? Moreover, what are the major applications?

Are there any instructions and directions for using a laser diode?

Which laser diodes characteristics are affected by a temperature change?

Are there any warnings to use Opnext laser diodes for medical applications?

What is polarization?

How is the polarization of Opnext Laser Diodes?

What is polarization ratio?

Is it possible to modulate the laser diode in pulse conditions? 

What is the the equivalent circuit of an internal laser diode?

Are Opnext laser diodes and Infrared Emitting Diodes (IREDs) compliant with RoHs?

What is the difference between a laser diode (LD) and an LED?

Though both laser diodes and LEDs are light outputting devices by injecting current, the light quality is quite different. The light emitted from an LED is a random phase light which is the same as other normal light, but the one emitted from a laser diode is phase matched (also known as coherent light), which allows it to have many unique applications.

Such coherent light can be a localized spot size after a collimated parallel and can be sent long distances while maintaining that localization.  Also, coherent light has interference characteristics so that it can be applicable to disc reading applications.  Moreover, because LDs can have a higher speed operation from LEDs, an LD is suitable for the applications in which a shortly pulsed light is needed. (e.g. a light source for optical pick-up of optical disc drive, light source for optical communication, etc.)

Are there any cautions for handling a Laser Diode?

Electrostatic discharge and electric spike input current should be prevented.  These may cause damage to the laser diode.  The test equipment and the operator should be properly grounded.

What are the applications of the infrared LED (IRED)?

IREDs are suitable for the light sources of the rotary encorders to control various industrial equipment and for the light sources of various sensors. 

Which safety standard do Opnext Laser Diodes comply with?

All Opnext LDs are registered with the FDA of the United States and each LD is classified into class II, IIIa, or IIIb according to the combination of the optical output power and wavelength values.  Please contact an Opnext sales office for details.  

What Laser Diode line up does Opnext have? Moreover, what are the major applications?

Opnext has two types of laser diodes. One is a visible LD and the other one is infrared LD.  The visible LDs are classified into three types of wavelength band - 635nm LD, 650 to 660nm LDs, and 670 to 690nm wavelength band LDs.  The 635nm LDs are suitable for laser pointers and levelers used in construction areas.  The 650 to 660nm LDs are suitable for the light sources for the optical pick-up in DVD disc drive equipment.  The 670 to 690nm LDs are suitable for the light sources of barcode scanners and various measurement equipment.  The infrared LDs have an 830nm wavelength which is invisible.  They are suitable for security sensors and other light source equipment.

Are there any instructions and directions for using a Laser Diode?

The LD characteristics are changeable by ambient temperature due to its semiconductor.  It is necessary to use proper heat dissipation techniques to operate LDs with more stability and reliability.

Which LD characteristics are changeable by a temperature change?

Optical output power changes significantly by temperature change.

An APC (Automatic Power Control) function is recommended for a LD drive circuit to achieve  stable operation.

Are there any warnings to use Opnext LDs for medical applications?

It is recommended to contact an Opnext sales office before using products in applications where its failure or malfunction may directly threaten human life or cause risk of bodily injury, such as aerospace, aeronautics, nuclear power, combustion control, transportation, traffic, safety equipment or medical equipment for life support. 

What is polarization?

Polarization is the light which vibrates only directions of certain electrical field and magnetic field.  There is no certain polarization in nature, but LD light is usually liner polarization.

Generally, polarization direction means the vibration surface of the electrical field.  In Laser Diodes, the vibration of the electrical field that is parallel to the active layer of the LD is called TE (Transverse Electric Wave) mode, and the vibration of the electrical field that is vertical to the active layer is called TM (Transverse Magnetic Wave) mode. 

How is the polarization of Opnext Laser Diodes?

Each LD has a TE mode or TM mode (Please refer to the above question) and every polarization direction for its package is different. It is recommended to contact an Opnext sales office when using LDs to the  application utilizing polarization.

What is polarization ratio?

The ratio can be found by dividing the parallel surface by the perpendicular surface. In LD is limitary because LD does not have complete linear polarization. This is called the polarization ratio.

It is different for LD and has a certain level of distribution.  It is recommended to contact an Opnext sales office when using LD to the application utilizing polarization.

Is it possible to modulate the Laser Diode in pulse conditions? 

It is possible to modulate an Opnext Laser Diode in pulse condition within absolute maximum ratings as specified by each LD.  (As for LD specified pulse output power, it is usable within absolute maximum power under specified pulse condition.)  Also available modulated pulse frequency depends on each LD. So It is recommended to ask an Opnext sales office for details when using an LD in pulse conditions.

What is the the equivalent circuit of an internal Laser Diode?

An equivalent circuit of an internal LD is shown below but circuit constants are different for each LD.  It is recommended to ask an Opnext sales office for details.

General equivalent circuit of internal LD

Are Opnext Laser Diodes and Infrared Emitting Diodes (IREDs) compliant with RoHs?

Yes. All Opnext LDs and IREDs are compliant with RoHs standards.