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Squeezed light from a semiconductor amplifier
Andrey S. Aleksandrov, Anatoly V. Masalov
TL;DR
The paper examines squeezed-light generation during strong-wave propagation through an amplifying semiconductor, where spontaneous-emission sidebands develop as symmetric two-mode squeezed components. Theoretical calculations model saturated semiconductor gain and four-wave mixing between a strong wave and weak spontaneous-emission sidebands. S0 = 1–1.5 is the input-intensity range where squeezing is maximal, squeezing increases monotonically with gain Z, and significant squeezing extends through Ωτe ≤1.
Problem
The paper examines squeezed-light generation during strong-wave propagation through an amplifying semiconductor, where spontaneous-emission sidebands develop as symmetric two-mode squeezed components.
Source: §I · p. 1Method
Theoretical calculations model saturated semiconductor gain and four-wave mixing between a strong wave and weak spontaneous-emission sidebands.
Source: §I · p. 1, §II · pp. 2–3Results
S0 = 1–1.5 is the input-intensity range where squeezing is maximal, squeezing increases monotonically with gain Z, and significant squeezing extends through Ωτe ≤1.
Source: §III · p. 5Takeaways & Limitations
The strong wave can serve as a local wave when recording the degree of squeezing.
Source: §I · p. 2The FWM effect weakens at low strong-wave intensity and disappears when Ω≫(1 + S)/τe.
Source: §II · p. 3
Abstract
from arXiv · showhide
The possibility of generating light in a squeezed quantum state during saturated light amplification in a semiconductor amplifier is theoretically analyzed. Due to four-wave mixing process during amplification, weak components of the spontaneous emission of the medium with symmetric frequency shifts relative to the strong amplified wave acquire the quantum properties of two-mode squeezed light. The squeezing of quadrature components occurs in the range of frequency shifts of several GHz ($\sim$ the inverse relaxation time of the charge carrier density) and can reach 10 dB or more under optimal conditions. The formation of a two-mode squeezing phase facilitates the observation of the squeezing effect, in which a strong wave, playing the role of a local wave, exhibits quadrature noise suppression without additional homodyne detection.
I. INTRODUCTION
The introduction contrasts transparency-region semiconductor squeezing with gain-region nonlinear dynamics, motivating saturated-amplifier four-wave mixing as a route to squeezing from weak sidebands. It also presents the strong amplified wave as a potential local wave for measuring squeezing.
I. INTRODUCTION
- Prior semiconductor demonstrations achieved 0.3–0.4 dB of squeezing in ZnSe and CdSe and required high-intensity femtosecond pulses, while AlxGa1−xAs calculations predicted 8.2 dB.The prediction was limited only by pump self-phase modulation.Source: §I · p. 1
- In semiconductor gain media, intensity-dependent carrier-density changes support four-wave mixing; the Bogatov effect gives weak red-shifted subthreshold modes a gain advantage over blue-shifted modes for frequency shifts within a carrier-relaxation-limited band.Source: §I · p. 1
- The paper theoretically analyzes whether four-wave mixing during amplification can squeeze weak spontaneous-emission sidebands symmetric about a strong wave.The introduction connects this proposed gain-medium process to four-wave mixing schemes used with dielectric media and Kerr-based microresonators.Source: §I · p. 1
- The strong amplified wave can serve as a local wave when recording the degree of squeezing.This is presented as an appeal of the proposed generation scheme.Source: §I · p. 2
II. SATURATED GAIN
Saturated amplification couples weak sidebands through four-wave mixing (FWM), enabling quadrature squeezing. The effect depends on intensity, gain, frequency, and Henry factor α.
II. SATURATED GAIN
- The model uses standard light–carrier-density equations, with saturation intensity normalizing the gain–inversion relationship and Z measuring unsaturated gain increment.The normalized coordinate gives S(Z) = S0eZ when radiation intensity is low and does not saturate inversion.Source: §II · p. 2
- The input comprises a strong wave and weak sidebands at symmetric frequency offsets, which originate as spontaneous radiation in the amplifier's input layers.During amplification, carrier-density inversion oscillates at the beat frequency Ω.Source: §II · p. 2
- The weak-mode relationships indicate that FWM can squeeze field fluctuations, with the quantum correspondence condition fulfilled at S ≫1.The analysis treats the coupled weak-mode equations as quantum solutions in the Heisenberg picture.Source: §II · pp. 3–4
- Except at α = 0, the blue-shifted weak mode gains less than |K|2 while the red-shifted mode gains more; the FWM effect grows with α.Figure 2 shows relative weak-mode energy gain for S0 = 1 and Z = 3 across Henry-factor values.Source: §II · p. 3, Figure 2 · p. 3
- The two-mode field's time-varying fluctuations characterize squeezing, and its minimum fluctuations are used to calculate the squeezing degree.The fluctuation signal contains a time-constant component and one oscillating at twice the frequency.Source: §II · pp. 4–5
- FWM is most relevant for S ≥1 and Z ≥1; it weakens at low strong-wave intensity and at frequencies Ω ≫ (1 + S)/τe.At S0 ≪1, M approaches zero and squeezing is zero.Source: §II · pp. 3–4
III. RESULTS
The calculations predict strongest squeezing near the optimal input intensity, with degree increasing with gain and decreasing at larger frequency shifts. Although the strong output wave can serve as a local wave, direct photodetection may reveal little squeezing or even anti-squeezing.
III. RESULTS
- The output contains a strong wave plus squeezed sideband pairs, but their saturated-amplification phase is far from optimal for direct detection, which reveals little squeezing or anti-squeezing.Source: §III · pp. 5–6
- ≈10 dB squeezing is reached at Z = 4 (e^Z = 55) and low frequencies Ωτe ∼1, with optimal input S0 = 1–1.5.Source: Figure 4 · p. 5, §III · p. 5
- At optimal input intensity, squeezing decreases as Ωτe grows, and significant squeezing extends through Ωτe ≤1.Source: Figure 5 · p. 5, §III · p. 5
IV. CONCLUSIONS
The estimates indicate that amplifying a strong quasimonochromatic wave in a semiconductor amplifier can generate squeezed light. Four-wave mixing converts spontaneous radiation into two-mode squeezed light in sidebands.
IV. CONCLUSIONS
- The estimates indicate squeezed-light generation when a strong quasimonochromatic wave is amplified in a semiconductor amplifier.Source: §IV · p. 6
- Four-wave mixing converts spontaneous radiation from the amplifying medium into two-mode squeezed light in sidebands.Source: §IV · p. 6