Optomechanical Nonlinearity in Dual-Nanoweb Structure Suspended Inside Capillary Fiber

Abstract

A novel kind of nanostructured optical fiber, displaying an extremely high and optically broadband optomechanical nonlinearity, is presented. It comprises two closely spaced ultrathin glass membranes (webs) suspended in air and attached to the inner walls of a glass fiber capillary. Light guided in this dual-web structure can exert attractive or repulsive pressure on the webs, causing them to be pushed together or pulled apart. The elastic deflection of the webs is, in turn, coupled to the electromagnetic field distribution and results in a change in the effective refractive index within the fiber. Employing a pump-probe technique in an interferometric setup, optomechanically induced refractive index changes more than 10^{4} times larger than the Kerr effect are detected. Theoretical estimates of the optomechanical nonlinearity agree well with the experimental results. The dual-web fiber combines the sensitivity of a microoptomechanical device with the versatility of an optical fiber and could trigger new developments in the fields of nonlinear optics, optical metrology, and sensing.

Fabrication of multiple parallel suspended-core optical fibers by sheet-stacking

“…The relative standard deviation of the thickness in the HF made by sheet-stacking approach is even twice as low as the one in the HF made from capillary-stacking method [18]. Note that because of lack of the information of the thickness variation for the dual-nanoweb fiber [16,17], the values listed in Table 1 were from a single-nanoweb fiber made by capillary stacking [18]. The dual-ASC fiber from the extrusion method shows the worst thickness uniformity of the membrane because of (i) the variation of the slot width (300-400 µm) on the metal die used for extrusion and (ii) the temperature gradient of the glass flow filling into the slot during the extrusion.…”

“…When an external force, such as air pressure [12], electrostatic actuation [13] or even optical force [14][15][16], is applied to one of the cores, the light coupling between the neighboring cores can be modified in a well-controlled manner. In order to allow the mechanical actuation of the cores by weak external forces and also to ensure low confinement loss of the cores, the supporting glass membranes are required to be longer than 10 μm and thinner than 200 nm.…”

“…Three major capillaries and four assisting capillaries were stacked inside a jacket tube (as shown in Fig.1(a)) and high air pressure was applied into these three major capillaries so that two thin and long membranes were finally formed in the fiber [16,17]. But it should be noted that there was no core formed in the fiber and the transmission loss at 1550nm was therefore measured to be 35dB/m, which is extremely high for silica based index-guided holey fibers.…”

Resolving the mystery of milliwatt-threshold opto-mechanical self-oscillation in dual-nanoweb fiber

“…13 It has been observed in a photonic crystal fiber with a solid core ∼1 µm in diameter and a vibrational frequency of a few GHz, 13 and also in a dual-nanoweb fiber structure with very strong optomechanical nonlinearity and a resonant frequency of ∼6 MHz. 14 Recently we reported mechanical self-oscillation of such a dual-nanoweb system when pumped by a few mW of narrow-line single-frequency laser light. 15 This came as a surprise, partly because in previous experiments a dual-frequency pump had always been needed to obtain oscillation, but also for a more subtle reason: Raman gain suppression.…”

Reconfigurable optical-force-drive chirp and delay line in micro- or nanofiber Bragg grating

“…Recent research into optomechanical effects in optical fibers mainly focused on one type of microstructured silica fiber: a dual-nanoweb structure suspended inside a capillary fiber. In dual-nanoweb structures, the strong optomechanical nonlinearity originating from a tight field confinement and a propagation length of several meters has been theoretically and experimentally investigated [8][9][10]. Nevertheless, the fabrication and implementation of related devices and their corresponding applications still present a significant challenge.…”