Phase matching condition of dual-pump phase-sensitive amplification in optical fiber

摘要

Phase-sensitive amplification (PSA) is a unique optical amplification scheme, featuring a low-noise property (i.e., quantum limited noise figure of 0 dB) and a phase clamping effect available for phase noise suppression [1]. It is based on optical parametric interaction between signal and pump lights. It is known that the interaction efficiency and then the signal gain depend on the phase matching between those interacting lights. There are typically two frequency arrangements for PSA in an optical fiber: (i) one pump (frequency: f_p) with signal (frequency: f_s) and conjugated idler (frequency: f_i) satisfying f_s + f_i = 2f_p [Fig. 1(a)], and (ii) two pumps (frequencies: f_p1, f_p2) with signal (frequency: f_s) satisfying f_p1 + f_p2 = 2f_s [Fig. 1(b)]. The phase matching condition for the former is well known, which is equivalent to that of phase-insensitive amplification where the signal light is amplified without an idler incident, such that the phase matching is satisfied when the center wavelength of interacting lights is in the normal dispersion region, i.e., a wavelength longer than the zero-dispersion wavelength of a fiber, as indicated in Fig. 1(a) [2]. On the other hand, the phase-matching condition for the latter has not been explicitly investigated, to the author's knowledge. Although several experimental demonstrations of dual-pump fiber PSA have been reported, many of them employed the wavelength allocation of the center wavelength being in the normal dispersion region, without detailed considerations on the phase matching [3-6]. Thereupon, this paper studies the phase matching condition of dual-pump PSA in an optical fiber.