Quantum dot laser
Encyclopedia
A quantum dot laser is a semiconductor laser that uses quantum dot
s as the active laser medium
in its light emitting region. Due to the tight confinement of charge carrier
s in quantum dots, they exhibit an electronic structure similar to atoms. Lasers fabricated from such an active media exhibit device performance that is closer to gas laser
s, and avoid some of the negative aspects of device performance associated with traditional semiconductor lasers based on bulk or quantum well
active media. Improvements in modulation bandwidth, lasing threshold
, relative intensity noise
, linewidth enhancement factor and temperature insensitivity have all been observed. The quantum dot active region may also be engineered to operate at different wavelengths by varying dot size and composition. This allows quantum dot lasers to be fabricated to operate at wavelengths previously not possible using semiconductor laser technology.
Recently, devices based on quantum dot active media are finding commercial application in medicine (laser scalpel
, optical coherence tomography
), display technologies (projection, laser TV
), spectroscopy and telecommunications. A 10 Gbit/s quantum dot laser that is insensitive to temperature fluctuation for use in optical data communications and optical networks has been developed using this technology. The laser is capable of high-speed operation at 1.3 μm wavelengths, at temperatures from 20 °C to 70 °C. It works in optical data transmission systems, optical LAN
s and metro-access systems
. In comparison to the performance of conventional strained quantum well laser
s of the past, the new quantum dot laser achieves significantly higher stability of temperature.
Quantum dot
A quantum dot is a portion of matter whose excitons are confined in all three spatial dimensions. Consequently, such materials have electronic properties intermediate between those of bulk semiconductors and those of discrete molecules. They were discovered at the beginning of the 1980s by Alexei...
s as the active laser medium
Active laser medium
The active laser medium is the source of optical gain within a laser. The gain results from the stimulated emission of electronic or molecular transitions to a lower energy state from a higher energy state...
in its light emitting region. Due to the tight confinement of charge carrier
Charge carrier
In physics, a charge carrier is a free particle carrying an electric charge, especially the particles that carry electric currents in electrical conductors. Examples are electrons and ions...
s in quantum dots, they exhibit an electronic structure similar to atoms. Lasers fabricated from such an active media exhibit device performance that is closer to gas laser
Gas laser
A gas laser is a laser in which an electric current is discharged through a gas to produce coherent light. The gas laser was the first continuous-light laser and the first laser to operate "on the principle of converting electrical energy to a laser light output...
s, and avoid some of the negative aspects of device performance associated with traditional semiconductor lasers based on bulk or quantum well
Quantum well
A quantum well is a potential well with only discrete energy values.One technology to create quantization is to confine particles, which were originally free to move in three dimensions, to two dimensions, forcing them to occupy a planar region...
active media. Improvements in modulation bandwidth, lasing threshold
Lasing threshold
The lasing threshold is the lowest excitation level at which a laser's output is dominated by stimulated emission rather than by spontaneous emission. Below the threshold, the laser's output power rises slowly with increasing excitation. Above threshold, the slope of power vs. excitation is orders...
, relative intensity noise
Relative intensity noise
Relative intensity noise , describes the instability in the power level of a laser. The noise term is important to describe lasers used in fiber-optic communication and LIDAR remote sensing....
, linewidth enhancement factor and temperature insensitivity have all been observed. The quantum dot active region may also be engineered to operate at different wavelengths by varying dot size and composition. This allows quantum dot lasers to be fabricated to operate at wavelengths previously not possible using semiconductor laser technology.
Recently, devices based on quantum dot active media are finding commercial application in medicine (laser scalpel
Laser scalpel
A laser scalpel is a scalpel for surgery, cutting or ablating living biological tissue by the energy of laser light. In soft tissue laser surgery, a laser beam ablates or vaporizes the soft tissue with high water content....
, optical coherence tomography
Optical coherence tomography
Optical coherence tomography is an optical signal acquisition and processing method. It captures micrometer-resolution, three-dimensional images from within optical scattering media . Optical coherence tomography is an interferometric technique, typically employing near-infrared light...
), display technologies (projection, laser TV
Laser TV
Laser color television , or Laser color video display utilizes two or more individually modulated optical rays of different colors to produce a combined spot that is scanned and projected across the image plane by a polygon-mirror system or less effectively by optoelectronic means to produce a...
), spectroscopy and telecommunications. A 10 Gbit/s quantum dot laser that is insensitive to temperature fluctuation for use in optical data communications and optical networks has been developed using this technology. The laser is capable of high-speed operation at 1.3 μm wavelengths, at temperatures from 20 °C to 70 °C. It works in optical data transmission systems, optical LAN
Local area network
A local area network is a computer network that interconnects computers in a limited area such as a home, school, computer laboratory, or office building...
s and metro-access systems
Metropolitan area network
A metropolitan area network is a computer network that usually spans a city or a large campus. A MAN usually interconnects a number of local area networks using a high-capacity backbone technology, such as fiber-optical links, and provides up-link services to wide area networks and the...
. In comparison to the performance of conventional strained quantum well laser
Quantum well laser
A quantum well laser is a laser diode in which the active region of the device is so narrow that quantum confinement occurs. The wavelength of the light emitted by a quantum well laser is determined by the width of the active region rather than just the bandgap of the material from which it is...
s of the past, the new quantum dot laser achieves significantly higher stability of temperature.