Subnatural Linewidth Biphotons with Controllable Temporal Length

Abstract

This Letter describes the generation of biphotons with a temporal length that can be varied over the range of 50-900 ns, with an estimated subnatural linewidth as small as 0.75 MHz. We make use of electromagnetically induced transparency and slow light in a two-dimensional magneto-optical trap with an optical depth as high as 62. We report a sharp leading edge spike that is a Sommerfeld-Brillouin precursor, as observed at the biphoton level.

Engineering biphoton wave packets with an electromagnetically induced grating

“…Different from previous findings [14][15][16][17][18]20,21,30], Eq. (12) clearly shows that the profile of the biphoton wave form is further manipulated by the periodic modulation of the control fields.…”

“…A recent demonstration of the generation of narrow-band biphotons in cold atomic ensembles via spontaneous four-wave mixing (SFWM) [14][15][16][17][18] has attracted considerable attention because of their long coherence time and controllable quantum wave packets. Nonlocal modulation of temporal correlation has been observed with such narrow-band biphotons [19].…”

Narrowband Biphotons: Generation, Manipulation, and Applications

“…In Fig. 9(b) the experimental demonstration of a near-rectangular-shape correlation is obtained at the optical depth around 53 [24]. The experimental parameters used here are γ 13 = γ 14 = 2π × 3 MHz, γ 12 = 0.02γ 13 , OD = 53, ∆ p = 48.67γ 13 , Ω p = 1.16γ 13 , and Ω c = 4.20γ 13 , respectively.…”

“…Suggested by Balic et al [33] and demonstrated by Du et al [24], the group delay regime is defined as τ g > τ r and the EIT slow-light effect can be used to control the biphoton temporal coherence time. The group delay condition is equivalent to Ω e > ∆ ω g ≈ 2π/τ g , i.e., the biphoton bandwidth is determined by phase matching.…”

“…In this chapter, we review recent advances in generating narrowband biphotons with long coherence time using forward-wave and backward-wave parametric interaction. In particular, we describe the monolithic resonant down-conversion with cluster effect [22,23] and the resonant SFWM in cold atoms with electromagnetically induced transparency (EIT) [24,25,26].…”