Questions about Lasers: Maser Substance & Wavelength Determination

[newbie7.07]

There are two questions I wanted to ask. The first is what substances are used in a maser? The second is how can the wavelength of a laser using a certain substance be determined without physical testing?

 

[mezarashi]

I've never studied MASERs, so I'll only comment on the second question.

LASERs are basically LEDs (light emitting diodes) with optical feedback, that is some type of resonator whether it be Distributed Feedback, Bragg, or through an external cavity. The wavelength of an LED depends on the materials' bandgap energy. The bandgap is characteristic to any material, so depending what color you'd like your laser to be, choose your weapon. LEDs generally have a energy spectrum spread of approximately 3kT, so additional frequency selection is done through the optical resonance. All of this can be done on paper before we take any action.

LEDs used to be limited to only infared and red. There was much difficulty in growing GaN on an appropriate substrate (has to do with epitaxial growth). But some decade ago, work by Nakamura and gang proved that it was possible. So now we have an entire visible spectrum of LEDs ^^

 

[Averagesupernova]

Lasers light is generated by far more than just the LED method. For instance, a CO2 laser is a tube filled with carbon dioxide which is then 'flooded' with RF energy. What typically happens inside a laser occurs with the CO2 laser also in that the light bounces back and forth end to end of the tube while its energy is steadily building then finally exits one end of the tube. A powerful enough CO2 laser typically can cut most common things other than metal and glass. Very common (probably exclusive) in the plastics cutting and engraving industry.

A YAG laser is another type. I know it is used in metal cutting and fabrication and I know it is an acronym for Yittrium Aluminum Garnett. I don't know much about it other than that and it is typically WAY more expensive to purchase than a CO2 laser.

There are other types but those are the ones I am familiar with. Go to www.synrad.com for more info.

 

[Danger]

There are two questions I wanted to ask. The first is what substances are used in a maser?

I'm digging up some 30 year-old memories here, and I'm not sure that they're right, but I seem to recall that the original masers were ammonia-based. If someone wants to do the math for bandgaps and whatnot, they can confirm or deny that.

 

[dlgoff]

Good memory Danger.

In 1951 Townes showed how useful radio waves only a centimeter long could be obtained form ammonia molecules.

http://www.richland2.k12.sc.us/rce/towneslz.htm"
Regards

 

[Astronuc]

http://en.wikipedia.org/wiki/Maser

Distinct names have been proposed for devices that emit in each portion of the spectrum, including grasers (gamma ray lasers), xasers (x-ray lasers), uvasers (ultraviolet lasers), lasers (visible lasers), irasers (infrared lasers), masers (microwave masers), and rasers (rf masers). Most of these terms never caught on, however. All but maser, laser, and raser are now obsolete, and the latter is uncommon.

I certainly remember uvaser in the "Star War/SDI" days.

Masers can be chemical (molecular) or solid state, just as lasers can be chemical (gas, e.g. He-Ne, CO₂, Excimer, etc) or solid state (e.g. ruby, YAG, etc). Excellent list of lasing materials - http://en.wikipedia.org/wiki/List_of_laser_types
See also Coherent Inc (nee Coherent General) - http://www.coherent.com/Lasers/

From the Bell Labs - Continuous Wave Solid-State Maser (Gd in La Ethylsulfate) was developed in 1956.

See also - http://www.lasing.com/paginas/archivos/his_nonlinear.htm