Abstract
We investigate theoretically the optical response of the output field and the tunable slow and fast light in a nonlinear optomechanical cavity with a degenerate optical parametric amplifier (OPA) and a higher order excited atomic ensemble. Studies show that the higher-order-excitation atom which is similar to the degenerate OPA that acts as a nonlinear medium, induces an additional dip in absorption spectrum of the probe field. The coherence of the mechanical oscillator leads to split the peak in absorption in the probe field spectrum so that the phenomenon of optomechanically induced transparency (OMIT) is generated from the output probe field. In particular, the presence of nonlinearities with the degenerate OPA and the higher order excited atoms can affect significantly the width of the transparency windows, providing an additional flexibility for controlling optical properties. Furthermore, in the presence of the degenerate OPA, the optical-response properties for the probe field become phase-sensitive so that a tunable switch from slow to fast light can be realized.
Highlights
We know the nonlinear optical effect of the optomechanical system can be obviously enhanced by adding a degenerate optical parametric amplifier (OPA)
In order to demonstrate the phenomenon of transparency and the group delay of the probe field in the system, we select the accessible parameters in optomechanical systems[43,60], i.e., the wavelength of the driving field λf ≈ 791 nm, the total cavity length L = 0.001 m, the total cavity decay rate κ = 2π × 215 × 103 Hz and κ0/κ = 0.5, the frequency of the moving mirror ωm = 2π × 947 × 103 Hz, the mechanical factor Q =ωm/γm = 6700, and the mass of the oscillating mirror m = 25 ng
We have studied a nonlinear optomechanical cavity with a degenerate OPA and a higher order excited atomic ensemble, which is driven by pump and probe laser fields
Summary
Where the first term describes the free Hamiltonian of cavity field and a (a†) is the annihilation (creation) operator of the cavity mode satisfying the commutation relation [a, a†] = 1. The second term is the free Hamiltonian of the atomic ensemble, where the ground state and the excited state of the ith two-level atom are described by |g〉(i) and. The last term in the first line denotes the interaction of the atomic ensemble with the driven cavity field, where g represents the averaged atom-field coupling strength[43,44,52]. The first term in the second line describes the coupling of the cavity mode with the degenerate OPA; GA is the nonlinear gain of the degenerate OPA, which is proportional to the pump amplitude, EOPA, i.e., GA =β|EOPA|; θ is the phase of the field driving the OPA28,46,47.
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