A laser diode (or LD) is a laser light emitting semiconductor device using the properties of a p-n junction. As laser diodes play an important role in optoelectronic applications, Egismos is proud to provide an extensive selection of laser diodes that include Infrared (IR) laser diode, Red laser diode, Green laser diode, Blue laser diode with various wavelengths, packages, and output powers. Egismos range of laser diodes comprises: 405nm, 450nm, 635nm, 650nm, 670nm, 780nm, 808nm, 830nm, 850nm, 870nm, 905nm, 980nm, 1064nm, 1310nm, 1550nm laser diodes from 3mW to 5W C-mount laser diodes.
The term laser is an acronym that stands for "Light Amplification by Stimulated Emission of Radiation". The laser diode structure and its basic elements structure are listed below.
EGISMOS currently markets GaN based blue laser diodes with wavelengths of 405nm and 450nm, green laser diodes (520nm wavelength), AlGaAs infrared laser diodes in the 780 - 980 nm wavelength range, as well as AlGaInP based red laser diodes in the 635 - 675 nm wavelength range. These laser diodes are highly rated in a broad range of applications. EGISMOS laser diodes are also compatible with multimedia and other new optical equipment on which the future of our advanced information society depends.
.A full line-up includes: index guided short-wavelength, low-noise, high output power
.Long life and high reliability
.A tabilized fundamental transverse mode
.3.8 mm, 5.6 mm diameter packages and frame type
.Pin connections compatible with various power supply systems
Lasing Modes of Laser Diode
Under laser oscillation, a light standing wave is created with its wave front parallel to the mirror facets while light is traveling back and forth within the laser cavity of laser diode. This standing wave consists of a longitudinal mode and two transverse modes (see below). The longitudinal mode expresses the condition of the standing wave in the direction of cavity length (z-direction). The transverse modes express the conditions of the axes perpendicular to the cavity length direction. The transverse modes are divided into a perpendicular transverse mode which is perpendicular to the active layer, and a parallel transverse mode which is parallel to the layer.
COD (Catastrophic Optical Damage) level
If the current is flowing toward the forward direction and the output keeps to rising after a kink or any kind of deviation, then the laser eventually reaches its facet breakdown (COD) level,at which point the crystal at the facet melts due to the high optical density. Special care must be taken in handling red laser diodes because they may keep oscillating with a low power of 2 to 3 mW even after a facet breakdown has occurred. There are several ways to tell whether an element is damaged or destroyed, such as through a far field pattern or an increase in the operating current. The life of a laser diode is significantly curtailed once the element is damaged, so special care must be taken to avoid not only exceeding current when adjusting the output power, but also surge like static electricity as well.
Optical and Electrical Characteristics 1
The limit values and the typical values of optical and electrical characteristics are described in this document as much as possible for users' convenience for application to electrical circuits and optics. The definitions of optical and electrical characteristics are listed below.
Optical and Electrical Characteristics 3 —Polarization Direction—
There are two types of polarization direction for the LDs, which are illustrated by Fig.A and Fig.B. The angles of the electric field and the magnetic field to the active layer are different from each laser diode to another.
Laser diode TM mode oscillation (See Fig.A), and TE mode oscillation laser diode (See Fig.B).
Polarizing characteristics of laser diodes vary with distortions in the active layer. Conventional infrared lasers as well as 650 to 675nm lasers oscillate in the TE mode (polarizing direction parallel to the junction plane). As such, special care must be taken when using polarized optical parts with 635nm laser because it oscillates in the TM mode (polarizing direction perpendicular to the junction plane).
Chip Position Accuracy
The limit values and the typical values of mechanical positions of a laser diode chip are described in this document according to users applications tand assembly requirements.
The definitions of the laser diode chip positions are listed below.
Precautions for use
1. Temperature characteristics
Laser characteristics (wavelength, operating current) vary with temperature, and variation is more extreme at shorter wavelength.
We recommend installing an APC circuit to maintain a constant output because operating current varies significantly with temperature.
By the same token, laser diodes reliability can be improved by designing products based on their heat release characteristics.
Since laser diode reliability falls off steeply at a higher temperature, never allow the case to exceed the operating temperature range given in specifications while a laser is in use.
2. Thermal radiation
Make sure that a thermal radiating plate (W 30 x L 30 x t 5 mm) made of aluminum or some other high thermal conducting materials is mounted to laser diode. The reliability of laser diode is closely linked to junction temperature, so reliability rapidly declines at a higher temperature. Do not overlook thermal radiation.
3. Measuring light output power
Use a light power meter to measure light output power of laser diodes. When measuring with APC drive, set a power meter at an angle as shown in the right figure so that a photodiode in a laser diode is not exposed to reflected light from the power meter.
Suitable handling precautions during device measurement and system design must be taken as described below for high performance of a device with high reliability.
The Absolute Maximum Ratings
When a laser diode is driven over its maximum ratings, instant breakdown or deterioration can occur, but also its reliability is considerably reduced in reliability.
Pay particular attention to the following points.
1. It is possible for laser diodes to be damaged by spike current, generated when switching the power ON or OFF or when adjusting its output voltage. Before activating diodes, check the transient state of the power supply to assure that it does not exceed the maximum voltage rating.
2. Operate the laser diodes below the maximum optical output power rating in order to prevent mirror facet damage and resultant loss in reliability.
3. The maximum ratings are specified by case temperature at 25˚C. Design should be made well to work with temperature. As temperature goes up, power dissipation as well as maximum light output power is reduced.
Maximum temperature is set at 260˚C and soldering time is within 3.0 seconds and minimum clearance of 1.6 mm from the root of a lead is necessary.
Prevention of breakdown due to static electricity or surge current
Laser diodes may be adversely affected by static electricity and surge current, which consequently causes breakdown of elements and reduction of their reliability unless the following actions cares are taken:
(1) Power supply, installation and measuring equipment should be grounded. A noise filter or noise-cut transformer is to be provided to power supply input utilized.
(2) During operation, working clothes, hats and shoes should be static-protected when in use. Also, a workman body should be static-protected by use of an earth-band or the like and grounded through high resistance (500K - 1M).
(3) A soldering iron should be grounded to protect laser diodes from voltage leak.
(4) Any container for carriage and storage should be static-protected. (5) Avoid using laser diodes at a place where high frequent surge current may be generated as an inductive electric field gives breakdown or deterioration. (Avoid being placed around fluorescent grow lamp, for example).
Electrostatic discharge and electric spike input which may damage the diodes should be prevented. The main causes of undesirable surge energy are static electricity on the human body, shipping containers made of unsuitable materials, abnormal pulses generated from test equipment, and voltage leakage from soldering irons.
1. Store diodes in temperature of between 5 and 30 degree and relative humidity of below 40%. Lower values of both are preferable. Avoid sharp drops in temperature in order to prevent condensation. It is recommended to store diodes in an atmosphere of dry nitrogen with a dew point of –40 degree.
2. Assure that the storage atmosphere is void of dust and gases harmful to diodes.
3. Use a storage case which can not easily be charged with static electricity.
Be sure to avoid direct exposure of human eyes to high power laser beams emitted from laser diodes. Even though barely visible and/or invisible to the human eye, they can be quite harmful. In particular, avoid looking directly into a laser diode or collimated beam along its optical axis when the diode is activated. One simple way to determine the optical path is to use a phosphor plate or infrared camera.
LD Package Handling
-G, -MG Types
1. Take care not to touch the window glass directly. Contamination and scratches on the window surface will result in deceased optical power output and distorted far field patterns. Contamination can usually be wiped off using a cotton swab with ethanol.
2. Do not squeeze the cap tightly, as it will cause the window glass to crack and package hermeticity to deteriorate.
3. Do not bend the bottom of the lead wire, as it will cause the glass area to crack and the hermeticity to deteriorate.
4. Do not cut or process package.
5. Mounting a diode on a thermal radiator
Laser diodes must be mounted on thermal radiators. For higher reliability, it is necessary to minimize mechanical stress to the packages and achieve sufficient heat sinking. Attention should be paid to the following items when mounting diodes on thermal radiators.
a. Use a copper or aluminum plate for the thermal radiator. The plate should be larger than 30 X 40 X 2 mm3.
b. To provide good thermal conductivity, polish the thermal radiator surface so that it will lie flat with the diode heat sink. Finish the radiator surface to keep bumps, twists, or bends below 0.05 mm.
c. Do not solder packages to thermal radiators, as this may result in excessive temperature to the assemblies inside the packages or loss of package hermeticity.
d. When mounting the diodes, do not touch or hit them against the caps, to prevent the window glass from becoming contaminated or cracked.
e. Do not use heat sink grease, as it may contaminate the window glass.
Prevention of Surge and ESD* for Laser Diodes
* Electric Static Damage
The laser diode is similare to other electronic devices and is very sensitive to static electricity and i. Accordingly, careful processes and measures are necessary. Here are some examples of ways to prevent surge destruction of laser diodes. See table-1.
For a basis model of electrostatic damage evaluation, two models (one human body model, one machine model) have been designed and the former is prescribed in MIL-STD-883C standards, and the latter is prescribed in EIAJ standards.
The ESD strength level is different from one laser diode to another. If you have any requirements on questions on this matter, please contact our product marketing dept.
LED are light emitting diodes made from a pn-junction that emits light when a suitable Voltage is applied to its leads. During this state, electrons recombine with holes within the semiconductor device, thereby releasing energy as photons (light particles). The color of the light is determined by the energy band gap of the semiconductor material used for the LED.
The laser diodes have a different structure in that the light is emitted inside a cavity within the semiconductor material. The cavity gives the laser diode its mains characteristics: the Coherence.
The laser light is coherent, which allows the laser to be focused into one tight spot. The laser beams can also stay narrow over great distance, which is called Collimation, which is unique among the light emitting devices. The laser light also has a high temporal coherence, which allows the light to be emitted with a very narrow spectrum (a few nanometers) as opposed to the LED, that emit with a wider spectrum.
The Wavelength is the spatial period of an electromagnetic radiation. Electromagnetic radiations with wavelengths in the range of 400nm to 700nm are perceived by human eye as visible light. Lasers usually show a very narrow wavelength spectrum. For the consumer market, they usually have a wavelength bandwidth of ~1nm, as opposed to conventional light sources that produce white light. White light corresponds to the sum of all visible and invisible (like infrared and UV) waves of the spectrum. A laser diode emits only at a determined wavelength emitted, depending on the semi-conductor material it is made out of..
A laser output power can be measured with a Power meter. Lasers can work in CW mode (continuous mode) or in a pulsed mode. Pulses power can be accounted on the basis of their average power or on the peak power of each pulse. Average lasers power ranges from <1mW for laser pointers and other consumer products to several kW for laser cutting applications or laser weapon systems, etc.
From the first lasers in 1964, it was clear that this light source has a power not only to do the required job, but also it can be very dangerous if operating improperly. Laser safety guidelines were written for consumers, power levels are usually written for visible-light, continuous-wave lasers and are divided into Class 1, Class 1M, Class 2, Class 2M, Class 3R, Class 3B, Class 4. For pulsed lasers and invisible wavelengths, other power limits might apply. In USA it is considered that Class2 lasers are safe for consumers, while EU requires lasers to be Class1. It is suggested for people working with class 3B and class 4 lasers to protect their eyes with safety goggles, which are designed to absorb light of a particular wavelength.
Laser light is coherent, which allows laser beams to be manipulated in order to create many different shapes, from simple collimated beams to complex patterns (created with DOE lenses). Most frequent patterns comprise: laser dot, round dot, laser line, laser cross, ground line. Custom patterns might be achieved through custom optical elements.
Lasers for consumer market can range from a few millimeters to bigger devices such as laser keyboards, laser scanners or laser projectors.
Many different fields can benefit from laser technology, such as: medicine, various industrial usages, military applications, consumer products, etc.... Nowadays usage of laser ranges from reading data from a CD or a DVD up to measuring the earth to moon distance.
|Product Code: Laser Diode||Package Diameter||Top(°C)||Wavelength Lambda(nm)||Output Power||Package Type|
|D: Laser Diode||3: TO Dia.3.3mm||4: 40||405: 405nm||3: 3mW||N:type|
|4: TO Dia.3.8mm||5: 50||450: 450nm||5: 5mW||P:type|
|6: TO-18 Dia.5.6mm||6: 60||635: 635nm||10: 10mW||M:type|
|9: TO-5 Dia.9.0mm||7:70||780: 780nm||50: 50mW|
|C:C-Mount||8: 80~85||808: 808nm||100: 100mW|
|850: 850nm||200: 200mW|
|980: 980nm||500: 500mW|
|1550: 1550nm||1W: 1000mW|