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Phase Transitions

Phase Transitions

Whether solid, liquid, or gas, a substance's state depends on the order and arrangement of its particles (atoms, molecules, or ions). Particles in the solid pack closely together, generally in a pattern. The particles vibrate about their fixed positions but do not move or squeeze past their neighbors. In liquids, although the particles are closely spaced, they are randomly arranged. The position of the particles are not fixed—that is, they are free to move past their neighbors to occupy...

Phase Transitions

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A phase transition is the process in which a substance changes from one state of matter to another, like from a solid to a liquid, liquid to gas, or vice versa, at a specific temperature and under given pressure conditions. This change is spontaneous and is affected by alterations in temperature and pressure. These parameters impact the strength of the forces between molecules (intermolecular forces) in the substance.During a phase transition, both the initial and final phases of the substance...

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Interference: Path Lengths

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Consider two sources of sound, that may or may not be in phase, emitting waves at a single frequency, and consider the frequencies to be the same.
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Related Experiment Video

Updated: Jun 19, 2026

Measurement of Quantum Interference in a Silicon Ring Resonator Photon Source

Measurement of Quantum Interference in a Silicon Ring Resonator Photon Source

Published on: April 4, 2017

Intersubband-transition-induced phase matching.

G Almogy, M Segev, A Yariv

|October 27, 2009

Summary

Researchers propose using quantum well intersubband transitions for phase matching in nonlinear materials. This method could significantly improve mid-infrared second-harmonic generation efficiency compared to bulk materials.

Area of Science:

Quantum optics
Materials science
Nonlinear optics

Background:

Phase matching is crucial for efficient nonlinear optical processes like second-harmonic generation.
Bulk materials like GaAs often exhibit phase mismatch, limiting conversion efficiency.
Quantum wells offer unique optical properties due to quantum confinement.

Purpose of the Study:

To investigate the use of refractive-index changes from intersubband transitions in quantum wells for phase matching.
To predict the potential improvement in second-harmonic generation (SHG) efficiency.
To analyze the role of linear phase contributions in SHG.

Main Methods:

Theoretical analysis of refractive-index changes associated with intersubband transitions.
Modeling of second-harmonic generation in quantum well structures.

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Related Experiment Videos

Last Updated: Jun 19, 2026

Measurement of Quantum Interference in a Silicon Ring Resonator Photon Source

Measurement of Quantum Interference in a Silicon Ring Resonator Photon Source

Published on: April 4, 2017

Measurement of Coherence Decay in GaMnAs Using Femtosecond Four-wave Mixing

Measurement of Coherence Decay in GaMnAs Using Femtosecond Four-wave Mixing

Published on: December 3, 2013

Patterning via Optical Saturable Transitions - Fabrication and Characterization

Patterning via Optical Saturable Transitions - Fabrication and Characterization

Published on: December 11, 2014

Comparison with non-phase-matched bulk GaAs.

Main Results:

Predicted improvement in mid-IR SHG conversion efficiency by nearly two orders of magnitude.
Demonstrated that linear phase contributions of intersubband transitions are critical.
Showcased how these contributions can either increase phase mismatch or achieve phase matching by offsetting bulk dispersion.

Conclusions:

Intersubband transitions in quantum wells offer a promising route for effective phase matching in nonlinear optics.
Careful consideration of linear phase contributions is essential for optimizing SHG efficiency.
Quantum wells present a viable alternative to bulk materials for enhanced nonlinear optical applications.