Related Experiment Video
Updated: Jun 8, 2026
16:11
Implementation of a Reference Interferometer for Nanodetection
Published on: April 26, 2014
Increased spatial frequency in interferential undulations of coupled cavity lasers
Applied Optics
|October 12, 2010
Summary
Researchers observed shorter light-output undulation periods in coupled cavity lasers. A multiple-mode model explains this phenomenon, confirmed by experiments with distributed feedback lasers.
Area of Science:
- Optics and Photonics
- Laser Physics
- Semiconductor Devices
Background:
- Coupled cavity lasers, including Fabry-Perot laser diodes, exhibit light-output undulations.
- The typical spatial period of these undulations is λ/2.
Purpose of the Study:
- To investigate and explain the observed increase in spatial frequency of light-output undulations in coupled cavity lasers.
- To theoretically model and experimentally verify the underlying physical mechanisms.
Main Methods:
- Experimental observation of interferential light-output undulation in coupled cavity lasers.
- Theoretical modeling using a multiple-mode approach.
- Experimental verification using a distributed feedback laser.
Main Results:
- Experimentally observed spatial frequencies corresponding to undulation periods of λ/4, λ/6, λ/8, and λ/10.
- Theoretical model successfully explains the increased spatial frequency by selecting a longitudinal mode with the lowest lasing threshold.
- Distributed feedback laser experiments confirmed the theoretical explanation, showing strong single-mode oscillation and a λ/2 spatial period.
Conclusions:
- The spatial frequency of light-output undulation in coupled cavity lasers can be significantly increased beyond the typical λ/2 period.
- A multiple-mode model provides a valid theoretical framework for understanding this phenomenon.
- Experimental validation confirms the role of mode selection in determining undulation periods.
Related Concept Videos
02:18Interference and Diffraction
Interference is a characteristic phenomenon exhibited by waves. When two electromagnetic waves interact with their peaks and troughs coinciding, a resulting wave with enhanced amplitude is produced. This is known as constructive interference. In this case, the two waves interacting are in phase with each other.
01:28Standing Waves in a Cavity
A household microwave and lasers are examples of standing electromagnetic waves in a cavity. When two conducting metal plates are placed parallel at the nodal planes, it creates a cavity where standing waves are formed. The cavity between the two planes is analogous to a stretched string held at the points x = 0 and x = L. Here, the distance 'L' between the two planes must be an integer multiple of half of the wavelength. The wavelengths that satisfy this condition are given by:
01:16Confocal Fluorescence Microscopy
Confocal microscopy is an advanced microscopic technique. The prime advantage of the confocal microscope over other microscopy techniques is its ability to block the out-of-focus light from the illuminated samples using pinholes. It is widely used with fluorescence optics to obtain high-resolution, sharp contrast images. Unlike optical microscopes, confocal microscopes use a focused beam of light laser to scan the entire sample surface at different z-planes. These microscopes are, therefore,...
01:07Interference and Superposition of Waves
When two waves of the same nature occur in the same region simultaneously, they result in interference. Interference of waves implies that the net effect of the waves is the sum of the individual waves' effects. However, it does not imply that the individual waves affect the propagation of other waves.
Interference occurs in mechanical waves, such as sound waves, waves on a string, and surface water waves. Mechanical waves correspond to the physical displacement of particles. Hence,...
Interference occurs in mechanical waves, such as sound waves, waves on a string, and surface water waves. Mechanical waves correspond to the physical displacement of particles. Hence,...
01:10Interference: Path Lengths
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.
Two special sources may be considered when they are in phase. This can be easily achieved by feeding the two sources from the same source. An example would be synchronizing the two speakers by feeding them with the same source, such as the sound waves produced by a tuning fork. This setup ensures that the two sources have the same frequency and are...
Two special sources may be considered when they are in phase. This can be easily achieved by feeding the two sources from the same source. An example would be synchronizing the two speakers by feeding them with the same source, such as the sound waves produced by a tuning fork. This setup ensures that the two sources have the same frequency and are...
00:53Sound Waves: Interference
Sound waves can be modeled either as longitudinal waves, wherein the molecules of the medium oscillate around an equilibrium position, or as pressure waves. When two identical waves from the same source superimpose on each other, the combination of two crests or two troughs results in amplitude reinforcement known as constructive interference. If two identical waves, that are initially in phase, become out of phase because of different path lengths, the combination of crests with troughs...