What is a Diode Laser?
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When an intrinsic semiconductor's electrical properties are altered by introducing impurities to the surface of a crystal wafer a laser diode is created. When semiconductor layers meet, charge carriers combine and the electrical current in the laser's energy is released as light, hence the name L.A.S.E.R. which stands for Light Amplification by the Stimulated Emission of Radiation. Advantages of diode lasers lie in their small size; laser diodes require little power to run, despite their high-power output.
A laser diode is an inexpensive, high power lasers with many capabilities. Diode lasers with wavelengths of 1310nm, 1550nm, and 1625nm are ideal for fiber optic communications, whereas diode lasers of 1480nm function well as pumps for optical amplifiers. However, there are other applications for laser diodes of these wavelengths, and many other wavelengths.
SemiNex Infrared Diode Lasers
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SemiNex Corporation makes and distributes infrared laser diodes between 1300nm and 1600nm (1.30µm to 1.60µm, or 1.30 to 1.60 micrometers),which are ideal for cosmetic applications such as acne removal, skin wrinkle reduction, and skin ablation and can also be used in a range of professional laser applications such as noninvasive surgery, free-space communications, and range finding. SemiNex lasers use high precision indium phosphide semiconductor materials to convert electrical energy directly and efficiently into coherent optical energy. SemiNex's proprietary material structure uses a non-conventional doping profile and a unique application of quantum physics that provides superior performance in thermal efficiency, electrical efficiency, and total optical power.
Types of Laser Diodes
Double Heterostructure Diode Laser
A double heterostructure diode laser is created when low bandgap material is fitted between two layers of high bandgap material. A bandgap is an energy range in a solid object without and electron states. Junctions between bandgap materials are referred to as "heterostructures." In a double heterostructure diode laser, the active region exists in the thin middle layer, allowing more electron-hole pairs to aid in light amplification.
Quantum Well Lasers
A quantum well is created when the middle layer is extremely thin, quantizing the vertical variation of the electron's wavefunction. Quantum well diode lasers have a good efficiency because the abrupt edge in the quantum well system concentrates electrons in energy states that contribute to laser action.
Quantum Cascade Diode Lasers
A quantum cascade laser utilizes the difference in quantum energy levels for the laser transition instead of using the bandgap, allowing for long and easily tuned wavelengths.
Separate Confinement Heterostructure Lasers
A separate confinement hetereostructure laser is made when two additional layers are added on the outside of a quantum well laser's original three layers. The middle layer in a quantum well laser can be too thin to confine light, so additional layers with a low refractive index have to be added in order to effectively confine light.
Distributed Feedback Lasers
A distributed feedback laser has a diffraction grating etched near the p-n junction in the diode to stabilize the wavelength. The grating is essentially an optical filter which causes a single wavelength to bounce back to the gain region and laser. In this system, facet reflection is no longer needed, so at least one facet in a distributed feedback laser is anti-reflection coated. These lasers have stable wavelengths because the wavelength is determined by the pitch of the grating.
Applications for Laser Diodes
Laser diodes can be used in a variety of industries. Applications for laser diodes at visible and infrared wavelengths include:- Free space optical communications
- Rangefinding
- Spectroscopic sensing
- LIDAR
- Aerospace welding
- Nonablative skin treatments
- Blood coagulation
- Noninvasive surgery
- Healing of wounds (heat/light therapy)
- CD/DVD reading technology
- Laser printing
Laser Diodes in Free Space Optics
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Free space optical communication is the transfer of data between two points with light as the transmission tool. When a laser diode (with an infrared wavelength) is used in free-space optical communications, the laser light's invisibility prevents interference and also has a low divergence (light does not "spread" as it travels). Many people do not know that they use optical communication technology daily, but infrared lasers are in many household controls. When you use the remote control to change the channel on your TV, an infrared diode laser in the remote sends binary-encoded information about which buttons you press to your TV, allowing you to change the channel or pause a movie.
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Diode Lasers in the Military
In the military, laser diodes are primarily used as laser target designators, which act as guides for precision-guided munitions. Because SemiNex's diode lasers are at infrared wavelengths between 1300nm and 1600nm, a SemiNex diode laser is favorable when directing munitions at live targets because light from an infrared laser diode cannot be detected by the human eye.
Laser Diodes in Temperature Measurement
Laser diodes can also be used in temperature measuring. Devices can aim laser light at an object and measure the electromagnetic radiation emitted from the object's surface. This is useful in situations where a contact-digital-thermometer would be dangerous or difficult to use, such as measuring the temperature of food on a grill or a car's engine.
Diode Lasers in the Cosmetic Industry
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Laser Diodes and their Potential to Treat Leishmaniasis
Leishmaniasis is a disease spread by sand flies which infects the blood and causes lacerations and wounds on the skin. These wounds are unresponsive to typical treatments for sores on the flesh and are only treatable when accurately diagnosed. If untreated, the wounds will eventually heal, generally after a year, but the disease continues to live in the blood stream and ultimately causes organ damage and failure. Research shows that heat therapy can help speed the process of wound healing, especially when used in conjunction with the traditional treatment for leishmaniasis, Sodium Stibogluconate. In the future, researchers hope to implement laser therapy in the treatment of cutaneous leishmaniasis to ease and quicken the recovery from the disease. It is possible that infrared diode lasers could provide heat therapy for treating leishmaniasis, although more research needs to be done to determine what wavelengths would be most beneficial to leishmaniasis healing. If infrared laser diodes do prove useful, the discovery would greatly benefit soldiers afflicted with leishmaniasis while overseas in the Middle East. Currently, soldiers diagnosed with leishmaniasis are flown out of combat areas (generally to Western Europe) for treatment which is both costly and prolonged. If laser light proved effective in treating leishmaniasis, a handheld product could be distributed to medical centers in combat areas, and the victims of leishmaniasis could be treated effectively on site.
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