A standard laser beam has photon degeneracy, or coherence, $\mathfrak{C}$ , of at most $8μ^2$ , where $μ$ is the number of photons in the laser itself. Even quantum-engineered lasers, if required to produce a beam with the standard statistical properties, have limited coherence, scaling as $μ^4$ . Moreover, such lasers (still unrealised) require very unconventional gain and output-coupling mechanisms. Here, we propose a different path to increasing $\mathfrak{C}$ : cascaded linear amplifiers, with conventional couplings. By dropping the requirement on the beam's properties, this approach can, in theory, achieve $\mathfrak{C}$ scaling exponentially in $μ$ . Here $μ$ is the total source excitation number, across all the amplifiers. Two amplifiers suffice to surpass the standard $μ^2$ scaling.A standard laser beam has photon degeneracy, or coherence, $\mathfrak{C}$, of at most $8μ^2$, where $μ$ is the number of photons in the laser itself. Even quantum-engineered lasers, if required to produce a beam with the standard statistical properties, have limited coherence, scaling as $μ^4$. Moreover, such lasers (still unrealised) require very unconventional gain and output-coupling mechanisms. Here, we propose a different path to increasing $\mathfrak{C}$: cascaded linear amplifiers, with conventional couplings. By dropping the requirement on the beam's properties, this approach can, in theory, achieve $\mathfrak{C}$ scaling exponentially in $μ$. Here $μ$ is the total source excitation number, across all the amplifiers. Two amplifiers suffice to surpass the standard $μ^2$ scaling.

quant-pharXiv:2607.28716Aug 3, 20260 citations

Second-order coherence properties of amplified spontaneous emission

Iliya V. Doronin, E. S. Andrianov, A. A. Zyablovsky +4 more

Properties of light sources based on amplified spontaneous emission (ASE) are similar to the properties of lasers in many regards. However, even though ASE has been widely studied, its photon statistics have not been settled. There are no reliable theoretical estimates or unambiguous experimental data for the second-order coherence function of photons that characterizes the coherence properties of a light source. Our computer simulation clearly establishes that, independently of pump power, the light produced by ASE is similar to that of a thermal source. This result lays bare the fundamental difference between ASE radiation and laser radiation.Properties of light sources based on amplified spontaneous emission (ASE) are similar to the properties of lasers in many regards. However, even though ASE has been widely studied, its photon statistics have not been settled. There are no reliable theoretical estimates or unambiguous experimental data for the second-order coherence function of photons that characterizes the coherence properties of a light source. Our computer simulation clearly establishes that, independently of pump power, the light produced by ASE is similar to that of a thermal source. This result lays bare the fundamental difference between ASE radiation and laser radiation.

Optics ExpressApr 4, 201928 citations

Coherence properties of matter-photon systems

道芳永島

Jan 1, 19780 citations

Coherence Properties of Matter‐Photon Systems

Michiyoshi Nagashima

Sep 25, 19780 citations

A standard laser beam has photon degeneracy, or coherence,

\mathfrak{C}

, of at most

8μ^2

, where

μ

is the number of photons in the laser itself. Even quantum-engineered lasers, if required to produce a beam with the standard statistical properties, have limited coherence, scaling as

μ^4

. Moreover, such lasers (still unrealised) require very unconventional gain and output-coupling mechanisms. Here, we propose a different path to increasing

\mathfrak{C}

: cascaded linear amplifiers, with conventional couplings. By dropping the requirement on the beam's properties, this approach can, in theory, achieve

\mathfrak{C}

scaling exponentially in

μ

. Here

μ

is the total source excitation number, across all the amplifiers. Two amplifiers suffice to surpass the standard

μ^2

scaling.