USHIO OPTO SEMICONDUCTORS (UOS) Product Q & A
Q1. What is the difference between laser diode (LD) and LED?
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.
On the other hand, LED has no threshhold current. so, it is easier to light it and helps drive circuit configuration simpler.
Q2. Are there any cautions for handling LD?
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.
Q3. Which safety standard does UOS LD comply with?
All UOS 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.
Q4. What LD lineup does UOS have? Moreover, what are those major applications?
UOS 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.
Q5. LAre there any instructions and directions for using LD?
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.
Q6. Which LD characteristics are changeable by the 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.
Q7. Are there any warnings to use UOS LDs for medical applications?
It is recommended to contact UOS 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.
Q8. 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 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.
Q9. How is polarization of UOS LD?
Each LD has TE mode orTM mode (Please refer to Q10) and every polarization direction for its packageis different. It is recommended tocontact to UOS sales office when using LDs to the application utilizingpolarization.
Q10. What is polarization ratio?
The ratio divided 2 surfaces in LD islimitary because LD is not complete linear polarization.
This is calledpolarization ratio.
It isdifferent by every LD and has certain level of distribution. It is recommended to contact to UOS salesoffice when using LD to the application utilizing polarization.
Q11. Is it possible to modulate the LD in pulse condition?
It is possible tomodulate UOS LD in pulse condition within absolute maximum ratings as specifiedby each LD. (As for LD specified pulseoutput power, it is usable within absolute maximum power under specified pulsecondition.) Also available modulatedpulse frequency depends on each LD. So itis recommended to ask UOS sales office for details when using LD in pulsecondition.
Q12. Could you inform the equivalent circuit of internal LD?
Equivalent circuit ofinternal LD is shown below but circuit constants are different by each LD. It is recommended to ask UOS sales office fordetails.
General Equivalent Circuitof Internal LD
Q13. Is UOS LD compliant with RoHS?
Yes it is.