Ultrafast Tunable Optical Delay Line Based on Indirect Photonic Transitions

Beggs, Daryl M.; Rey, Isabella H.; Kampfrath, Tobias; Kuipers, L.; Krauss, Thomas F.

doi:10.1103/physrevlett.108.213901

Cited by 50 publications

(44 citation statements)

References 22 publications

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“…Indirect photonic transitions in a photonic crystal waveguide have now also been demonstrated in a two-step process [5], and offer exciting opportunities for ultrafast delay applications [5,17]. Here, we study indirect photonic transitions that occur in a single step and investigate the parameter space required for tuning their magnitude.…”

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confidence: 99%

“…The process of inducing a frequency and a wave vector shift on an optical signal, such that it undergoes a transition between two modes of a photonic structure, has been referred to as an indirect photonic transition in the recent literature [1][2][3][4][5]. Indirect photonic transitions are not only of fundamental physical interest, but may constitute the operating principle for the realization of integrated nonreciprocal optical isolators without using magneto-optical effects [4].…”

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confidence: 99%

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Optically Induced Indirect Photonic Transitions in a Slow Light Photonic Crystal Waveguide

et al. 2014

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We demonstrate indirect photonic transitions in a silicon slow light photonic crystal waveguide. The transitions are driven by an optically generated refractive index front that moves along the waveguide and interacts with a signal pulse copropagating in the structure. We experimentally confirm a theoretical model which indicates that the ratio of the frequency and wave vector shifts associated with the indirect photonic transition is identical to the propagation velocity of the refractive index front. The physical origin of the transitions achieved here is fundamentally different than in previously proposed refractive index modulation concepts with fixed temporal and spatial modulation frequencies; as here, the interaction with the refractive index front results in a Doppler-like signal frequency and wave vector shift. Consequently, the bandwidth over which perfect mode frequency and wave vector matching is achieved is not intrinsically limited by the shape of the photonic bands, and tuning of the indirect photonic transitions is possible without any need for geometrical modifications of the structure. Our device is genuinely nonreciprocal, as it provides different frequency shifts for co-and counterpropagating signal and index fronts.

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Optically Induced Indirect Photonic Transitions in a Slow Light Photonic Crystal Waveguide

et al. 2014

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“…Quasi-indirect photonic transitions in a photonic crystal waveguide have now also been demonstrated in a two-step process, where the frequency shift is realized first, followed by a shift of the wave vector [5]. This approach is still applicable for tunable delay but does not have all the properties of the indirect transition.…”

Section: Introductionmentioning

confidence: 99%

“…The process of an optical signal undergoing a transition between two modes of a photonic structure is referred to as a photonic transition [1][2][3][4][5]. Photonic transitions can be direct, if the optical signal experiences a shift in frequency but not in wave vector, or indirect, if both frequency and wave vector of the signal are changed.…”

Section: Introductionmentioning

confidence: 99%

“…Further, they offer exciting opportunities for ultrafast delay applications [5,14]. In this context, indirect photonic transitions between modes that belong to different photonic bands, called indirect interband transitions, have attracted attention, since a cascade of transitions, and thus the appearance of multiple frequency components, can be avoided [15,[2][3][4].…”

Section: Introductionmentioning

confidence: 99%

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Indirect transitions of a signal interacting with a moving refractive index front

et al. 2014

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The dynamic manipulation of light can be achieved by the interaction of a signal pulse propagating through or reflected from a refractive index front. Both the frequency and the wave vector of the signal are changed in this case, which is generally referred to as an indirect transition. We have developed a theory to describe such transitions in integrated photonic crystal waveguides. Through indirect transitions, the following effects can be envisaged: large frequency shifts and light stopping and order of magnitude pulse compression and broadening without center frequency shift. All effects can be potentially realized with a refractive index modulation as small as 0.001.For the experimental realization, we have used slow light photonic crystal waveguides in silicon. The refractive index front was obtained by free carriers generation with a switching pulse co-propagating with the signal in the same slow light waveguide. The group velocities of the signal and the front could be varied arbitrarily by choosing the right frequencies of the signal and switching pulses. The indirect transition was unambiguously demonstrated by considering two situations: a) the front overtaking the signal and b) the signal overtaking the front. In both cases, a blue shift of the signal frequency was observed. This blue shift can only be explained by the occurrence of the expected indirect transition and not by a direct transition without wave vector variation.

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Linear Terahertz Frequency Conversion in a Temporal‐Boundary Metasurface

Xu,

Xing,

et al. 2024

Laser & Photonics Reviews

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Linear frequency conversion enabled by a temporal boundary of a resonant cavity provides a promising alternative to generating new frequency components, where the temporal boundary can be introduced by rapidly modifying the refractive index of the cavity. However, the perturbed photon dynamics during the ultrafast linear process is still vague. Here, the photon dynamics based on temporal coupled‐mode theory are explored and the phenomena are demonstrated with a silicon metasurface via simulations and experiments in the terahertz regime. With the time‐varying real and imaginary parts of the refractive index, a periodic modulation (Td) of the amplification coefficient of the newly generated photons is observed where the optimized coefficient occurs in the first period at td = Td /2. It further establishes a dynamic critical coupling condition to improve the amplification coefficient in the dynamic process. The scheme of linear frequency conversion via temporal boundary can revolutionize the paradigm of parametric amplification from nonlinear to linear processes, and conversion efficiency will be improved in a high‐quality factor cavity. The ultrafast modulation will find applications in optical signal processing, modulators, and reconfigurable intelligent surfaces for development of the next‐generation communications.

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Ultrafast Tunable Optical Delay Line Based on Indirect Photonic Transitions

Cited by 50 publications

References 22 publications

Optically Induced Indirect Photonic Transitions in a Slow Light Photonic Crystal Waveguide

Optically Induced Indirect Photonic Transitions in a Slow Light Photonic Crystal Waveguide

Indirect transitions of a signal interacting with a moving refractive index front

Linear Terahertz Frequency Conversion in a Temporal‐Boundary Metasurface

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