Project Ideas

Laser Stabilization

Longitudinal Modes in Lasers Stabilized Single Frequency HeNe


This is another topic that I am quite interested in. Standing sound waves in crystals create a diffraction grating which affects any light that passes through. crystals

In this article, researchers use acousto-optics to test for contaiminants in liquids. That sounds like a good potential project to me.

Light Pulses

Some lasers are operated in pulsed mode. Pulses tend to have high peak powers and a large wavelength range. There are various methods to produce pulses. Q-switching involves altering the conditions of the laser cavity. A gain is allowed to build up and a switch in the Q (lasing conditions) will release a strong pulse. Cavity dumping involves the use of an acousto-optic device within the lasing cavity which when activated, will divert a short pulse of light. The output mirror on the laser in this case is replaced by a high-reflective mirror similar to the mirror at the other end of the laser cavity. Mode-locking is a process that involves the resonant modes inside the laser cavity. Interference allows the production of a train of pulses.

Unfortunately, fancy non-He-Ne lasers are needed to produce strong pulses and they are not available in the lab. It is possible to produce pulses using He-Ne but it seems most articles describe it as a proof-of-concept thing more than something with potential applications.

Diffraction and Zone Plates

Sinusoidal Zone
Sinosoidal Zone Plae

The scientists of the past were amazing discoverers, doing so much during their lives. Take Fresnel who discovered and investigated many, many things such as the things he is now named for such as Fresnel (nearfield) diffraction and Fresnel lenses. Anyway, these innovations were pretty amazing. I wanted to put Zone Plates on this page because this was the topic I initially considered investigating back in May/June when I first looked to join the LTC. Zone plates are structures consisting of alternating transparent and opaque concentric rings. They act as lenses, but work on the principle of diffraction, not refraction. This can be advantageous for focusing light of wavelengths that are affected little by refraction by glass.

Although I will probably not be investigating this topic, I am glad Nityan has and he has done much math work simulating the operation of these diffraction lenses that I don't think I could have done. Link

Victor Zhao
June 2008
Laser Teaching Center