# Glossary of Terms

Disclaimer *These are terms I am currently trying to define and understand and by no means are the actual textbook definition, but I try to get close.*

Adiabatic Rapid Passage-"ARP" A coherent process that relies on stimulated emission, controlled by the properties of the laser. When utilizing pulsed, frequency swept laser light one can impart forces an order of magnitude greater than traditional optical forces. Recent experiments have be conducted by changing the intensity of the light and the amplitude of the frequency modulation.

Adiabatic Theorem- A theory that says a quantum mechanical system subjected to a gradually changing external condition will adapt its functional form, but if subjected to a rapidly varying condition there is insufficient time for the functional form to adapt, and the probability density remains the same.

Amplitude Modulator-This utilizes an interferometry technique to modulate the signal. The device has two arms where the input signal is split according to the strength of a DC signal. The split signals then run down each arms which are wave guides. Then a RF signal changes the indices of refraction of each wave guide so when the two waves recombine they will interfere depending on the RF signal and the ratio of the signals that went down each arm.

Bichromatic Force-A technique of laser cooling by which carefully orchestrated, rapid, coherent sequence of absorptions followed by stimulated emissions from a non-monochromatic light impart a force on the atoms. Utilizing two lasers separated in frequency by an equal amount plus/minus resonance this force is achieved. The force is much stronger and spans a much larger velocity range than the ordinary radiative force that been used for laser cooling.

Brownian Motion-The random motion of moving particles in a fluid. This is a result from the bombardment of fast-moving atoms or molecules in the fluid. It is also used as a mathematical model used to describe random events such as fixational eye movements, solutions to Laplace's equation, and to estimate harmonic measure.

Counter-Intuitive Order-The key behind the efficiency of STIRAP, the ~796nm laser associated with the 33P2->n=15+ interacts with the atomic beam first then the ~389nm laser associated with the 23S1->33P2 with overlap between the two beams. As an analogy when climbing a ladder, to reach step 3 one doesn't step from 2 to 3 then 1 to 2, hence the name counter-intuitive. The reason for this is associated with the underlying quantum mechanics of the system that show that the intermediate state 33P2 is never populated in this three state system.

Doppler Molasses-A laser cooling technique that has been found able to cool atoms to temperatures very near 0K at maximum efficiency. This occurs when counterpropagating beams or circularly polarized light created a standing wave where the light polarization depends on the spatial location. In this standing wave, atoms moving with a velocity climb a polarization gradient hill, in doing so they lose their velocity. At the top of the hill, atoms are resonant with the molasses beam and absorb a photon, decay into a lower magnetic sub-level and have to climb the hill again.

Multi-Channel Plate-Used to detect particles, this device is used to give location-specific based information on the particles that bombard it. The impact of a charged particle starts a cascade of electrons that propagate through the channel, amplifying the signal by several orders of magnitude. The design consists of a channel withing a honeycomb structure.

Phase Modulation-A form of modulation inwhich an RF signal changes the index of refraction of a wave guide. Therefore when as an input signal travels through the wave guide, its phase is shifted due to the change in indices of refraction.

Pockels Effect-The effect where an applied electric signal (constant or varying) produces a birefringence in an optical medium. This is not to be confused with the Kerr effect where, in this case, the birefringence is proportional to the electric field, and the Kerr effect is quadratic to the field. In our lab, this effect is utilized in the phase modulator. As the light passes through a medium, the different index of refraction will impart a phase shift on the light. In the amplitude modulator, we essentially use two phase modulators where about half the light goes into both, and later recombined such that the two interfere.

Rydberg State-An excited atom with one or more electrons having a very high principal quantum number n>15. These atoms have such characteristic features as having a large electric dipole moment, the electron wavefunctions can be approximated by classical orbits of the electrons about the nuclei and a long lifetime.

Stark Shift-Is the shifting and splitting of spectrial lines of atoms and molecules due to the presence of an external static electric field. An electrical analogue of the Zeeman effect.

Stimulated Rapid Adiabatic Passage-"STIRAP" A procedure found to obtain 100% population transfer, is our case it is from the metastable ground state of He and the Rydberg state. This is achieved by a sequence of two lasers at ~796nm and ~389nm separately. in the counter-intuitive order. The key is that the intermediate state 33P2 is never populated.

Wave Guide-This structure utilizies a material to guide electromagnetic waves through. In our case the wave guides we use are crystalline structures because of their lattice structures. The geometry of the wave guide is very important, for example a slab waveguide confines energy to travel only in one dimension. The frequency of the transmitted wave also dictates the shape of the waveguide, as a rule of thumb the width of the waveguide needs to be the same order of magnitude as the wavelength of the guided wave.