What is spectral linewidth?

Spectral linewidth is a measure of the spectral content of the laser light. The fundamental value for the spectral linewidth is given by the Shawlow-Townes expression which is essentially the contribution to the linewidth due to phase changes from spontaneous emission processes.

What is narrow-linewidth laser?

The term narrow-linewidth lasers usually applies to single-frequency lasers, i.e., lasers oscillating on a single resonator mode with low phase noise and thus with high spectral purity. Typically, such lasers also exhibit low intensity noise.

How many modes can lase simultaneously?

Since the width of the gain curve (FWHM) is only 1400MHz, only two longitudinal modes can operate at any given time. If the laser were twice as long, four longitudinal modes could operate simultaneously.

How is spectral linewidth calculated?

The spectral width caused by phase noise is commonly referred to as spectral linewidth, which is proportional to the rate of spontaneous emission and inversely proportional to the photon density: Δ ω ∝ R sp / ( 2 P ) .

How do you calculate the linewidth of a laser?

The linewidth (or line width) of a laser, e.g. a single-frequency laser, is the width (typically the full width at half-maximum, FWHM) of its optical spectrum. More precisely, it is the width of the power spectral density of the emitted electric field in terms of frequency, wavenumber or wavelength.

Which led structure has narrow spectral width?

Superradiant LEDs have very narrow emission spectra, typically 1-2% of the central wavelength and offer power levels rivaling a laser diode. These devices are popular for fiber optic gyroscope applications. The second type of LED is the surface emitter.

How do you calculate mode spacing?

1. The difference between frequencies of adjacent.
2. modes (mode spacing) is equal to the basic.
3. frequency of the cavity: (Δν) = c/(2nL)

How do you calculate coherence length?

Waves with wavelength λ and λ + Δλ, which at some point in space constructively interfere, will no longer constructively interfere after some optical path length lc = λ2/(2πΔλ); lc is called the coherence length. [The phase of a wave propagating into the x-direction is given by φ = kx – ωt.

Is the linewidth the same as the spectral shape?

This shows that the linewidth alone, or even the linewidth complemented with a spectral shape (line shape), does by far not provide full information on the spectral purity of laser light. (This is particularly the case for lasers with dominating low-frequency phase noise.)

What are the benefits of narrower spectral linewidth?

Narrower spectral line-width and smaller frequency chirping enable a larger number of communication channels by reducing the pulse spreading in digital systems and reducing signal distortion in analog systems, which are all influenced by the fiber dispersion.

What is the α parameter in linewidth enhancement?

The α parameter is also called the amplitude-phase coupling factor. The name linewidth enhancement factor emphasizes that it leads to a spectral linewidth enhancement. The name amplitude-phase coupling factor emphasizes its physical origin.

What is the spectral linewidth of a Fabry Perot laser?

The spectral linewidth of standard Fabry–Perot semiconductor lasers is typically on the order of 100 MHz. For many applications, such as holography, spectroscopy, and coherent optical communication systems, these broad linewidths are unsatisfactory.