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What is the working principle of semiconductor laser?
The principle of semiconductor laser is very different from CO2 and Nd:YAG lasers. It is based on "Recombination Radiation" The semiconductor materials have valence band V and conduction band C, the energy level of conduction band is Eg (Eg>0) higher than that of valence band. To make things simple, we start our analysis supposing the temperature to be 0 K. It can be proved that the conclusions we draw under 0 K applies to normal temperatures. Under this assumption for nondegenerate semiconductor, initially the conduction band is completely empty and the valence band is completely filled. Now we excite some electrons from valence band to conduction band, after about 1 ps, electrons in the conduction band drop to the lowest unoccupied levels of this band, we name the upper boundary of the electron energy levels in the conduction band the quasi-Fermi level Efc. Meanwhile holes appear in the valence band and electrons near the top of the valence band drop to the lowest energy levels of the unoccupied valence energy levels, leave on the top of the valence band an empty part. We call the new upper boundary energy level of the valence band quasi-Fermi level Efv. When electrons in the conduction band run into the valence band, they will combine with the holes, in the same time they emit photons. This is the recombination radiation. Our task is to make this recombination radiation to lase
What is the black band in Back to the Future in the 50s?
Chuck berry
What band does Cleveland go on tour with?
Black Box later renamed Blackbox
Who sings monochrome no kiss for black butler?
The band Sid (シド) sings this song
What is the music video of a band that has a guy lead singer it is real people then switches to animated its in black and white and when its animated it looks like someone is drawing the people?
pie band
What materials radiate heat?
All materials radiate heat equivalent to their temperature above absolute zero.This heat is called "black body" radiation. When the peak of the "black body" radiation from a material is in the infrared band we perceive it as heat, but the radiation is always radiant heat regardless of whether it peak is in the radio band, infrared band, visible band, ultraviolet band, x-ray band, etc.
Why are heat sinks black?
Well, they aren't always black. Heatsinks that depend mostly on convection or forced air to dispose of waste heat can be any color.However a heatsink that depends in large part on radiation to dispose of waste heat should be black. This is because the ideal emitter/absorber of radiation is a blackbody. A blackbody emits an ideal continuous spectrum of electromagnetic radiation with a peak at the high end of the band and no missing frequencies in that band. If the color is not black there are missing frequencies and the radiation is not the most efficient it could be.
Possibility of holes in conduction band?
hoes are vacancies left by the electron in the valence band. hence there cannot be holes in the conduction band
Why cant there be hole current in the conduction band?
In a semiconductor, the conduction band is filled with electrons, which are negatively charged. Holes represent the absence of electrons in the valence band, not in the conduction band. Since the conduction band is typically occupied by electrons, it cannot have holes; instead, holes exist in the valence band where electrons are missing. Therefore, while there can be free electrons in the conduction band, holes are specifically a feature of the valence band.
What is heavy hole light hole and split-off hole?
the occupied highest band is the heavy band, the band prior below it is ligh band, the distance between two extremal points of those band is split-off band. At those points, hole is situated to be corresponding holes.
How is light created from a black hole?
No light comes from a black hole. There are occasional bursts of X-rays from the accretion disk AROUND the black hole, we believe, caused as dust and gas are accelerated by gravity to nearly the speed of light. That's what we call the "event horizon"; the point at which falling mass is accelerated to lightspeed. Since the math for matter traveling at lightspeed doesn't make any sense, we say "We CAN'T know what happens". Eventually, many years from now, we'll be able to examine the area around a black hole, but there are none nearby. EVERYTHING we think we know about black holes is based on mathematical theory, and it is highly probable that much of what we think we know is wrong. Unfortunately, we don't know which parts.
What is a bandshape?
A bandshape is a shape of a band of electromagnetic radiation.
What is the working principle of semiconductor laser?
The principle of semiconductor laser is very different from CO2 and Nd:YAG lasers. It is based on "Recombination Radiation" The semiconductor materials have valence band V and conduction band C, the energy level of conduction band is Eg (Eg>0) higher than that of valence band. To make things simple, we start our analysis supposing the temperature to be 0 K. It can be proved that the conclusions we draw under 0 K applies to normal temperatures. Under this assumption for nondegenerate semiconductor, initially the conduction band is completely empty and the valence band is completely filled. Now we excite some electrons from valence band to conduction band, after about 1 ps, electrons in the conduction band drop to the lowest unoccupied levels of this band, we name the upper boundary of the electron energy levels in the conduction band the quasi-Fermi level Efc. Meanwhile holes appear in the valence band and electrons near the top of the valence band drop to the lowest energy levels of the unoccupied valence energy levels, leave on the top of the valence band an empty part. We call the new upper boundary energy level of the valence band quasi-Fermi level Efv. When electrons in the conduction band run into the valence band, they will combine with the holes, in the same time they emit photons. This is the recombination radiation. Our task is to make this recombination radiation to lase
When was Black Cobra - band - created?
Black Cobra - band - was created in 2002.
When was Black Ice - band - created?
Black Ice - band - was created in 1999.
When was Black Widow - band - created?
Black Widow - band - was created in 1969.
When was Black Mountain - band - created?
Black Mountain - band - was created in 2004.
