Technical Support Information (Laser)

A1.
Though both LD and LED are light output coming device by injecting current, the light quality is quite different.  The light emitted from LED is a random phase light which is same as other normal light, but the one emitted from LD is phase matched so called coherent, and it cases to many unique applications.
Such coherent light can be localized spot size after collimated parallel and be sent long distance with kept this localization.  Also coherent light has interference characteristics so that it can be applicable to disc reading application.  Moreover, because LD can be high-speed operation generally from LED, 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.)
 

A2.
Electrostatic discharge and electric spike input current should be prevented.  These may cause to damaged LD.  The test equipments and operators body should be grounded properly.
 

A3.
All Ushio LDs are registered in FDA of United States and each LD is classified into class II, IIIa, IIIb, or  Ⅳaccording to the combination of the optical output power and wavelength values.  Please contact sales office for details.

A4.
Ushio has two types of LD.  One is visible LD and other one is infrared LD.  The visible LDs are classified into four types of wavelength band, 400nm LD, 635 nm LD, 650 to 660 nm LDs, and 670 to 690 nm wavelength band LDs. The 400nm LDs are suitable for direct imaging application. The 635 nm LDs are suitable for display and levelers used in construction area.  The 650 to 660 nm LDs are suitable for the light sources of medical and sensor equipments.  The 670 to 690 nm LDs are suitable for the light sources of barcode scanners and various measurement equipments.  The infrared LDs have 830 to 850 nm wavelength which is invisible.  They are suitable for security sensors and other various light source equipments.

A5.
The LD characteristics are changeable by ambient temperature due to its semiconductor essential.  It is necessary to take account of good enough heat dissipation design to operate LDs more stable and reliable.
 

A6.
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.
 

A7.
It is recommended to contact Ushio sales office before using product in applications which 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.
 

A8.
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 electrical field.  In LD, the vibration of electrical field directed parallel to active layer of LD is called TE (Transverse Electric Wave) mode, as directed to vertical to active layer is called TM (Transverse Magnetic Wave) mode.
 

A9.
Each LD has TE mode or TM mode (Please refer to Q10) and every polarization direction for its package is different.  It is recommended to contact to Ushio sales office when using LDs to the application utilizing polarization.
 

A10.
The ratio divided 2 surfaces in LD is limitary because LD is not complete linear polarization.
This is called polarization ratio.
It is different by every LD and has certain level of distribution.  It is recommended to contact to Ushio sales office when using LD to the application utilizing polarization.
 

A11.          
It is possible to modulate Ushio LD 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 Ushio sales office for details when using LD in pulse condition.
 

A12.          
Equivalent circuit of internal LD is shown below but circuit constants are different by each LD.  It is recommended to ask Ushio sales office for details.
 

A13.
Yes it is.