Large Brillouin amplification in silicon

Abstract

Strong Brillouin coupling has only recently been realized in silicon using a new class of optomechanical waveguides that yield both optical and phononic confinement. Despite these major advances, appreciable Brillouin amplification has yet to be observed in silicon. Using a new membrane-suspended silicon waveguide we report large Brillouin amplification for the first time, reaching levels greater than 5 dB for modest pump powers, and demonstrate a record low (5 mW) threshold for net amplification. This work represents a crucial advance necessary to realize highperformance Brillouin lasers and amplifiers in silicon.Both Kerr and Raman nonlinearities are radically enhanced by tight optical-mode confinement in nanoscale silicon waveguides [1][2][3][4]. Counter-intuitively, Brillouin nonlinearities are exceedingly weak in these same nonlinear waveguides [5]. Only recently have strong Brillouin interactions been realized in a new class of optomechanical structures that control the interaction between guided photons and phonons [5][6][7]. With careful design, such Brillouin nonlinearities overtake all other nonlinear processes in silicon [6,7]; these same Brillouin interactions are remarkably tailorable, permitting a range of hybrid photonic-phononic signal processing operations that have no analog in all-optical signal processing [8][9][10][11][12]. Using this physics, the rapidly growing field of silicon-based Brillouin-photonics has produced new frequency agile RFphotonic notch filters [8,10,13,14] and multi-pole bandpass filters [12] as the basis for radio-frequency photonic (RF-photonic) signal processing. Beyond these specific examples, the potential impact of such Brillouin interactions is immense; frequency combs [13,15,16], ultra-low phasenoise lasers [17][18][19], sensors [9,12,20], optical isolation [21][22][23][24], and an array of signal processing technologies [8,[12][13][14][25][26][27]] may be possible in silicon with further progress.However, strong Brillouin amplification-essential to many new Brillouin-based technologies-has yet to be realized in silicon photonics. Despite the creation of strong Brillouin nonlinearities in a range of new structures [6,7], nonlinear losses and free carrier effects have stifled attempts to demonstrate net optical amplification. Only recently, Van Laer et al. reported 0.5 dB (12%) amplification [28] using suspended silicon nanowire structures. Even with superb dimensional control, amplification diminishes with longer interaction lengths [28], highlighting the problem of dimensionally induced inhomogenous broadening [29]. Careful theoretical analyses by Wolff et al., suggest that large net amplification is fundamentally challenging to achieve in silicon nanowires at near-IR wavelengths due to nonlinear absorption [30].In this paper, we report large Brillouin amplification in silicon through an alternative device paradigm; using a new all-silicon membrane structure (Fig. 1) that permits independent design of photonic and phononic modes, we demonstrate net amplification a...

Enhanced Brillouin amplification in Si

“…These tasks can include light emission as in the case of organic light-emitting diodes (OLEDs) 2 , the conversion of sunlight to electrical energy as in organic photovoltaics (OPVs) 3,4 , fieldeffect current modulation as in organic field-effect transistors (OFETs) 5 , and current modulation and light emission in organic light-emitting transistors (OLETs) 6 . Now, writing in Nature Nanotechnology, Leydecker et al 7 add to this arsenal with the demonstration of a stable multilevel organic memory device (OMD) that is controlled by light.…”

Invited Article: Acousto-optic finite-difference frequency-domain algorithm for first-principles simulations of on-chip acousto-optic devices

“…[1][2][3] Traditionally, SBS has been studied extensively in fiber-optic devices in order to inhibit undesired nonlinear effects induced by SBS. [1][2][3][4] More recently, SBS has been tailored for micron-scale on-chip devices, 2,3,[5][6][7][8][9][10] where it is considered to be an attractive candidate in the creation of lasers with ultra-narrow bandwidths, [11][12][13][14] gigahertz frequency combs, 15,16 slow light, 17 and on-chip signal processing devices such as the microwave photonic filter 18,19 and optical isolators. [20][21][22][23] Given the wide range of devices that can harness SBS, it is important to develop general numerical techniques that can facilitate the device design process.…”

“…As such, when designing fiber-optic and on-chip acousto-optic devices, researchers typically adopt a mode-expansion technique, which calculates the optical and acoustic modes independently and then treats the acousto-optic coupling perturbatively using the coupled mode theory. [5][6][7][8][9][10][11][12][13]16,[18][19][20][21] Unfortunately, the application of coupled mode theory is not exact and becomes difficult for complex geometries, which may support a large number of interacting modes. Therefore, in order to accurately and realistically perform first-principles simulations of a general class of acousto-optic devices, there is an urgent need to develop a computational algorithm to efficiently and exactly simulate the interactions between optical and acoustic waves.…”

Reconfigurable and frequency-agile on-chip microwave photonic bandpass and bandstop filters using stimulated Brillouin scattering

“…Using very low values of gain and the concept of RF signal interference, notch filters with very high suppression have been achieved on a photonic chip [7]. Also, on-chip SBS has also been demonstrated in silicon [8,9] and hybrid silicon structures [10] with gain being limited to sub-10 dB. In this work, we present our recent breakthrough in the fabrication and design of chalcogenide chips to enhance the light-sound interaction resulting in an on-chip gain of 40 dB.…”