Intense Squeezed Light from Lasers with Sharply Nonlinear Gain at Optical Frequencies

Linh Nguyen, Jamison Sloan, Nicholas Rivera, and Marin Soljačić

Phys. Rev. Lett. 131, 173801 – Published 23 October 2023

Abstract

Nonclassical states of light, such as number-squeezed light, with fluctuations below the classical shot noise level, have important uses in metrology, communication, quantum information processing, and quantum simulation. However, generating these nonclassical states of light, especially with high intensity and a high degree of squeezing, is challenging. To address this problem, we introduce a new concept which uses gain to generate intense sub-Poissonian light at optical frequencies. It exploits a strongly nonlinear gain for photons which arises from a combination of frequency-dependent gain and Kerr nonlinearity. In this laser architecture, the interaction between the gain medium and Kerr nonlinearity suppresses the spontaneous emission at high photon number states, leading to a strong “negative feedback” that suppresses photon-number fluctuations. We discuss realistic implementations of this concept based on the use of solid-state gain media in laser cavities with Kerr nonlinear materials, showing how 90% squeezing of photon number fluctuations below the shot noise level can be realized.

Received 8 April 2023
Accepted 26 September 2023

DOI:https://doi.org/10.1103/PhysRevLett.131.173801

Physics Subject Headings (PhySH)

Nonlinear optics Quantum optics

Atomic, Molecular & Optical

Authors & Affiliations

Linh Nguyen ^1,*, Jamison Sloan², Nicholas Rivera^1,3, and Marin Soljačić¹

¹Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02138, USA
²Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02138, USA
³Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA

^*linhnk@mit.edu

Article Text (Subscription Required)

Click to Expand

Supplemental Material (Subscription Required)

Click to Expand

References (Subscription Required)

Click to Expand

Issue

Vol. 131, Iss. 17 — 27 October 2023

Reuse & Permissions

Access Options

Article part of CHORUS

Accepted manuscript will be available starting 22 October 2024.

Author publication services for translation and copyediting assistance advertisement

Images

Figure 1
A laser based on Kerr nonlinearity. (a) A pumped gain medium coupled to a cavity with Kerr nonlinearity. (b) Four-level atoms in the gain medium, with lasing transition between level 3 and 2 with frequency $ω_{0}$ . The dashed lines show the dependence of the cavity resonance frequency $ω_{c} (n)$ (blue) and the spontaneous emission rate $R_{sp}$ (green) on the light intensity of an “off-resonant Kerr laser” ( $ω_{c} - ω_{0} = Δ_{0}$ ), and the solid lines are those of “resonant Kerr laser” ( $ω_{c} = ω_{0}$ ). (c) The photon number probability distribution [ $p (n_{1})$ and $p (n_{2})$ ] depends on the angle between the gain ( ${R_{sp} (n) Λ / [γ_{∥} + R_{sp} (n) n]}$ ) and the loss ( $κ_{1}$ and $κ_{2}$ ) at their intersection point (or the steady state). Because the gain intersects with the loss $κ_{1}$ at intensity $n_{1}$ more steeply than with the loss $κ_{2}$ at intensity $n_{2}$ , the probability distribution at $n_{1}$ is more squeezed, thus, the photon number variance is reduced.
Reuse & Permissions
Figure 2
Output characteristics of a resonant Kerr laser. Parameters used for an Nd:YAG based system are $γ_{⊥} = 10^{12} s^{- 1}$ , $γ_{∥} = 4.34 \times 10^{3} s^{- 1}$ , $κ = 10^{7} s^{- 1}$ , and the coupling coefficient $g = 10^{2} s^{- 1}$ . For figures (a), (b), and (c), lines with the same color and line style have the same $β$ values. (a) Steady-state photon number of a Kerr laser as a function of relative pump rate $r$ for different nonlinear coefficients. (b) Time evolution of photon number at different nonlinear coefficients and at fixed relative pump rate $r = 150$ . (c) The Fano spectrum [noise spectrum in frequency domain ( $ω$ ) or intensity] at different nonlinear coefficients and at fixed relative pump rate $r = 150$ and their corresponding Fano factors $F$ . (d) Fano factor $F$ at different pump rates as a function of nonlinear coefficient. At small $β$ value, $F$ can be approximated by $(κ^{2} γ_{⊥} / 2 Λ g^{2})$ (dotted line). For large enough $β$ , $F$ approximately equals to $| R_{sp} (n_{s}) / R_{sp}^{'} (n_{s}) n_{s} |$ (dashed line). As $β$ becomes much larger than $\sqrt{(κ g^{2} γ_{⊥} / 2 Λ γ_{| |})}$ , $F$ approaches the sub-Poissonian value of 0.5.
Reuse & Permissions
Figure 3
Off resonant nonlinear Kerr laser with Nd:YAG gain medium and the detuning value between the gain medium and the zero photon cavity being $Δ_{0} = 10^{13} s^{- 1}$ . (a) The gain and loss rate as functions of light intensity at different pump rates and at fixed nonlinear coefficient $β = 10 s^{- 1}$ . (b) The number of steady solutions depends on both the nonlinear coefficient and pump rate. (c) Fano factor $F$ at different pump rates as a function of nonlinear coefficient. $F$ reaches a global minimum value of $[γ_{⊥} / (γ_{⊥} + Δ_{0})]$ when the detuning value between the cavity and the gain medium $- Δ_{0} + β n_{s}$ equals the gain bandwidth $γ_{⊥}$ . At small $β$ value, $F \approx κ^{2} Δ_{0}^{2} / (2 Λ g^{2} γ_{⊥})$ (dotted lines). For large enough $β$ value, $F \approx | R_{sp} (n_{s}) / R_{sp}^{'} (n_{s}) n_{s} |$ (dashed lines).
Reuse & Permissions

Physical Review Letters