Showing papers on "Slow light published in 2010"
TL;DR: In this paper, the authors describe the way in which strongly modulated photonic crystals differ from other optical media, and clarify what they can do, including light confinement, frequency dispersion and spatial dispersion.
Abstract: Recently, strongly modulated photonic crystals, fabricated by the state-of-the-art semiconductor nanofabrication process, have realized various novel optical properties. This paper describes the way in which they differ from other optical media, and clarifies what they can do. In particular, three important issues are considered: light confinement, frequency dispersion and spatial dispersion. First, I describe the latest status and impact of ultra-strong light confinement in a wavelength-cubic volume achieved in photonic crystals. Second, the extreme reduction in the speed of light is reported, which was achieved as a result of frequency dispersion management. Third, strange negative refraction in photonic crystals is introduced, which results from their unique spatial dispersion, and it is clarified how this leads to perfect imaging. The last two sections are devoted to applications of these novel properties. First, I report the fact that strong light confinement and huge light–matter interaction enhancement make strongly modulated photonic crystals promising for on-chip all-optical processing, and present several examples including all-optical switches/memories and optical logics. As a second application, it is shown that the strong light confinement and slow light in strongly modulated photonic crystals enable the adiabatic tuning of light, which leads to various novel ways of controlling light, such as adiabatic frequency conversion, efficient optomechanics systems, photon memories and photons pinning.
403 citations
TL;DR: Evidence of an anomalously high density of photonic states in hyperbolic metamaterials is observed, which demonstrates the feasibility of an earlier-predicted single-photon gun, and paves the road for the use of metammaterials in quantum optics.
Abstract: We have observed, in metamaterial with hyperbolic dispersion (an array of silver nanowires in alumina membrane), a sixfold reduction of the emission lifetime of dye deposited onto the metamaterial’s surface. This serves as evidence of an anomalously high density of photonic states in hyperbolic metamaterials, demonstrates the feasibility of an earlier-predicted single-photon gun, and paves the road for the use of metamaterials in quantum optics.
346 citations
TL;DR: In this article, different types of dispersion engineered photonic crystal waveguides have been developed for slow light applications, and the group index bandwidth product (GBP) and the loss per delay in terms of dB ns −1 were compared.
Abstract: We review the different types of dispersion engineered photonic crystal waveguides that have been developed for slow light applications. We introduce the group index bandwidth product (GBP) and the loss per delay in terms of dB ns −1 as two key figures of merit to describe such structures and compare the different experimental realizations based on these figures. A key outcome of the comparison is that slow light based on photonic crystals performs as well or better than slow light based on coupled ring resonators.
231 citations
01 Jan 2010
TL;DR: In this paper, the authors presented a method with experimental demonstrations for improving the maximum fractional delay of a slow-light medium using a multiple-gain-line medium and showed that the spectral sensitivity of slow light media is proportional to the group index of the medium inside the slow light medium.
Abstract: "Slow and fast light" constitute a broad class of
science and technology that
can dramatically change the group
index of a medium over a certain wavelength
range. This thesis is
composed of studies regarding both fundamental aspects and
applications of slow light.
The thesis starts with some discussion
on two fundamental questions. The first
one is how much momentum a
photon carries within a slow-light medium, and what
kind of force
is experienced by a slow-light medium when a photon enters or
leaves it.
The second issue is how the noise properties of an
optical field change as it propagates
through a slow-light
medium.
The second part of the thesis deals with the applications
of slow light for tunable
time delays. For such applications, one
of the key figures of merit is the maximum
fractional delay that a
slow-light element can achieve. I first present a method with
experimental demonstrations for improving the maximum fractional
delay using a
multiple-gain-line medium. Second, I present a
design with experimental demonstration for how to achieve
simultaneous tunable delay and advancement using slow and
fast
light in a single module. I then propose a design of a digitally
tunable module
using channelized slow light, which can be useful
for optical packet delays, etc.
The third part of the thesis
studies the use of slow light to enhance the performance of
spectroscopic interferometers. I start with the derivation of the
spectral
sensitivity of two-beam and multiple-beam interferometers
with slow-light media incorporated in them. I show both
theoretically and experimentally that the spectral
sensitivity is
proportional to the group index of the medium inside the
interferometers.
Second, I propose and demonstrate experimentally
a new type of Fourier-transform
interferometer using tunable slow
light. I then analyze the performance of three types
of slow-light
media for interferometry applications. Lastly, I present a design
of an on-chip slow-light spectrometer as well as some studies on
slow-light waveguides using
photonic crystal
structures.
196 citations
TL;DR: A theoretical model is developed that accurately describes the loss spectra of PhC waveguides and reveals that the entire hole contributes coherently to the scattering process, in contrast to previous models that added up the scattering from short sections incoherently.
Abstract: Slow light devices such as photonic crystal waveguides (PhCW) and coupled resonator optical waveguides (CROW) have much promise for optical signal processing applications and a number of successful demonstrations underpinning this promise have already been made. Most of these applications are limited by propagation losses, especially for higher group indices. These losses are caused by technological imperfections ("extrinsic loss") that cause scattering of light from the waveguide mode. The relationship between this loss and the group velocity is complex and until now has not been fully understood. Here, we present a comprehensive explanation of the extrinsic loss mechanisms in PhC waveguides and address some misconceptions surrounding loss and slow light that have arisen in recent years. We develop a theoretical model that accurately describes the loss spectra of PhC waveguides. One of the key insights of the model is that the entire hole contributes coherently to the scattering process, in contrast to previous models that added up the scattering from short sections incoherently. As a result, we have already realised waveguides with significantly lower losses than comparable photonic crystal waveguides as well as achieving propagation losses, in units of loss per unit time (dB/ns) that are even lower than those of state-of-the-art coupled resonator optical waveguides based on silicon photonic wires. The model will enable more advanced designs with further loss reduction within existing technological constraints.
195 citations
TL;DR: A planar design of a metamaterial exhibiting electromagnetically induced transparency that is amenable to experimental verification in the microwave frequency band is presented and interpreted in terms of two linearly coupled Lorentzian resonators.
Abstract: We present a planar design of a metamaterial exhibiting electromagnetically induced transparency that is amenable to experimental verification in the microwave frequency band. The design is based on the coupling of a split-ring resonator with a cut-wire in the same plane. We investigate the sensitivity of the parameters of the transmission window on the coupling strength and on the circuit elements of the individual resonators, and we interpret the results in terms of two linearly coupled Lorentzian resonators. Our metamaterial designs combine low losses with the extremely small group velocity associated with the resonant response in the transmission window, rendering them suitable for slow light applications at room temperature.
161 citations
TL;DR: In this article, the physical basics of slow light propagation in atomic media, photonic structures, and optical fibers are considered and a set of criteria are then used to compare different media.
Abstract: I consider the physical basics of slow light propagation in atomic media, photonic
structures, and optical fibers. I show similarities and differences between all of
the above media and develop set of criteria that are then used to compare different
media. Special attention is given to dispersion of group velocity and loss, which are
shown to limit the bandwidth and delay capacity of all the slow light schemes.
157 citations
TL;DR: This work demonstrates optical performance monitoring of in-band optical signal to noise ratio (OSNR) and residual dispersion, using slow-light enhanced optical third harmonic generation (THG) in a compact 2D silicon photonic crystal waveguide, and opens the door for slow light to play a key role in ultra-high bandwidth telecommunications systems.
Abstract: We demonstrate optical performance monitoring of in-band optical signal to noise ratio (OSNR) and residual dispersion, at bit rates of 40Gb/s, 160Gb/s and 640Gb/s, using slow-light enhanced optical third harmonic generation (THG) in a compact (80µm) dispersion engineered 2D silicon photonic crystal waveguide. We show that there is no intrinsic degradation in the enhancement of the signal processing at 640Gb/s relative to that at 40Gb/s, and that this device should operate well above 1Tb/s. This work represents a record 16-fold increase in processing speed for a silicon device, and opens the door for slow light to play a key role in ultra-high bandwidth telecommunications systems.
156 citations
TL;DR: In this article, a summary of recent experiments showing how various nonlinear phenomena are enhanced due to slow light in silicon photonic crystal waveguides is presented, including self-phase modulation (SPM), two-photon absorption (TPA), free-carrier related effects, and third-harmonic generation.
Abstract: We present a summary of our recent experiments showing how various nonlinear phenomena are enhanced due to slow light in silicon photonic crystal waveguides. These nonlinear processes include self-phase modulation (SPM), two-photon absorption (TPA), free-carrier related effects, and third-harmonic generation, the last effect being associated with the emission of green visible light, an unexpected phenomenon in silicon. These demonstrations exploit photonic crystal waveguides engineered to support slow modes with a range of group velocities as low as c/50 and, more crucially, with significantly reduced dispersion. We discuss the potential of slow light in photonic crystals for realizing compact nonlinear devices operating at low powers. In particular, we consider the application of SPM to all-optical regeneration, and experimentally investigate an original approach, where enhanced TPA and free-carrier absorption are used for partial regeneration of a high-bit rate data stream (10 Gb/s).
151 citations
TL;DR: In this paper, a planar metamaterial exhibiting classical electromagnetically induced transparency (EIT) was used to demonstrate that an EIT-like resonance can be achieved without breaking the symmetry of the structure.
Abstract: We report on our experimental work concerning a planar metamaterial exhibiting classical electromagnetically induced transparency (EIT). Using a structure with two mirrored split-ring resonators as the dark element and a cut wire as the radiative element, we demonstrate that an EIT-like resonance can be achieved without breaking the symmetry of the structure. The mirror symmetry of the metamaterial's structural element results in a selection rule inhibiting magnetic dipole radiation for the dark element, and the increased quality factor leads to low absorption (<10%) and large group index (of the order of 30).
144 citations
TL;DR: The results, supported by numerical simulations, emphasize the importance of engineering the dispersion of PhC waveguides to exploit the slow light enhancement of FWM efficiency, even for short device lengths.
Abstract: We experimentally investigate four-wave mixing (FWM) in short (80 μm) dispersion-engineered slow light silicon photonic crystal waveguides. The pump, probe and idler signals all lie in a 14 nm wide low dispersion region with a near-constant group velocity of c/30. We measure an instantaneous conversion efficiency of up to −9dB between the idler and the continuous-wave probe, with 1W peak pump power and 6nm pump-probe detuning. This conversion efficiency is found to be considerably higher (>10 × ) than that of a Si nanowire with a group velocity ten times larger. In addition, we estimate the FWM bandwidth to be at least that of the flat band slow light window. These results, supported by numerical simulations, emphasize the importance of engineering the dispersion of PhC waveguides to exploit the slow light enhancement of FWM efficiency, even for short device lengths.
TL;DR: In this article, a silicon/organic hybrid modulator integrating photonic crystal (PC) waveguide, 75 nm slot, and electro-optic (EO) polymer is experimentally demonstrated.
Abstract: A silicon/organic hybrid modulator integrating photonic crystal (PC) waveguide, 75 nm slot, and electro-optic (EO) polymer is experimentally demonstrated. Slow light in PC waveguide and strong field confinement in slot waveguide enable ultraefficient EO modulation with a record-low Vπ×L of 0.56 V mm and an in-device effective r33 of 132 pm/V. This result makes it the most efficient EO polymer modulator demonstrated to date. The modulated signal shows strong wavelength dependence and peak enhancement of 23 dB near the band edge of defect mode, which confirms the signature of the slow light effect.
TL;DR: In this paper, the authors acknowledge the support from the BrainBridge project ZJU-TU/e and Philips Research collaboration, and the National Natural Science Foundation of China Grant No. 60907018.
Abstract: The authors acknowledge the support from the BrainBridge
project ZJU-TU/e and Philips Research collaboration,
AOARD, and the National Natural Science Foundation of
China Grant No. 60907018.
TL;DR: In this paper, the authors demonstrate theoretically and numerically that tunable slow light can be realized in planar semiconductor metamaterials with the unit cell composed of two different elements in a broad terahertz regime.
Abstract: We demonstrate theoretically and numerically that tunable slow light can be realized in planar semiconductor metamaterials with the unit cell composed of two different elements in a broad terahertz regime. In the unit cell, one element is a semiconductor split ring resonator and another one is a semiconductor cut wire. The interaction between the two elements of the unit cell, induced directly or indirectly by the incident electromagnetic wave, leads to a transparent window, resembling the classical analog of electromagnetically induced transparency. This transparent window, caused by the coupling of bright-bright modes or dark-bright modes, can be continuously tuned in a broad frequency regime. The strong normal phase dispersion in the vicinity of this transparent window results in the slow light effect. This scheme provides an alternative way to achieve tunable slow light in a broad frequency band and can find important applications in active and reversibly tunable slow light devices.
TL;DR: The generated true time delay is analyzed as a promising solution to feed phased array antenna for radar systems and to develop dynamically reconfigurable microwave photonic filters.
Abstract: We experimentally demonstrate a novel technique to process broadband microwave signals, using all-optically tunable true time delay in optical fibers. The configuration to achieve true time delay basically consists of two main stages: photonic RF phase shifter and slow light, based on stimulated Brillouin scattering in fibers. Dispersion properties of fibers are controlled, separately at optical carrier frequency and in the vicinity of microwave signal bandwidth. This way time delay induced within the signal bandwidth can be manipulated to correctly act as true time delay with a proper phase compensation introduced to the optical carrier. We completely analyzed the generated true time delay as a promising solution to feed phased array antenna for radar systems and to develop dynamically reconfigurable microwave photonic filters.
TL;DR: In this article, the authors show that the incorporation of thin layers made of an active medium adjacently to the core layer of a negative-refractive-index waveguide can completely remove dissipative losses in a slow-light regime where the effective index of the guided horizon wave is negative.
Abstract: We review recent theoretical and experimental in progress in the realisation of slow and stopped light by the 'trapped
rainbow' principle in optical metamaterials featuring negative electromagnetic parameters (permittivity/permeability
and/or refractive index). We explain how and why these structures can enable complete stopping of light even in the
presence of disorder and, simultaneously, dissipative losses. Using full-wave numerical simulations we show that the
incorporation of thin layers made of an active medium adjacently to the core layer of a negative-refractive-index
waveguide can completely remove dissipative losses - in a slow-light regime where the effective index of the guided
wave is negative.
TL;DR: In this paper, the authors describe the underlying theory developed for shallow gratings, but whose conclusions can be extended to planar photonic crystal waveguides, in particular the enhancement of third-order nonlinear processes with slow light.
Abstract: We review recent advances related to slow light in periodic structures, where the refractive index varies along one or two directions, i.e. gratings and planar photonic crystals. We focus on how these geometries are conducive to enhancing the nonlinear interaction between light and matter. We describe the underlying theory developed for shallow gratings, but whose conclusions can be extended to planar photonic crystal waveguides, in particular the enhancement of third-order nonlinear processes with slow light. We review some experiments showing how gratings have been used for pulse compression and the generation of slow gap solitons. We then present recent nonlinear experiments performed in photonic crystal waveguides that demonstrate the strong reinforcement of nonlinear third-order optical phenomena with slow light. We discuss the challenges associated with slow light in these 2D structures and their unique advantage—dispersion engineering—for creating broadband nonlinear devices for all-optical signal processing. By breaking down the relation between dispersion and group velocity imposed in gratings, these structures also offer new opportunities for generating soliton-like effects over short length scales, at low powers and with short pulses.
TL;DR: In this article, a planar planar atomic spectroscopy chip with hot rubidium atoms in hollow-core waveguides was used to demonstrate the ability to reduce the group velocity of light by a factor of 1,200.
Abstract: The ability to slow down the propagation of light touches both fundamental aspects of light–matter interactions and practical applications in photonic communication and computation1,2,3. Optical quantum interference can substantially reduce the speed of light while offering additional dramatic optical effects based on the ability to control electronic quantum states4,5. Recent efforts are increasingly being directed towards harnessing these effects in integrated photonic structures6,7. Here, we report the first demonstration of slow light and electromagnetically induced transparency in a self-contained, planar atomic spectroscopy chip. Using hot rubidium atoms in hollow-core waveguides, we demonstrate 44% optical transparency with a group index of 1,200, or more than sevenfold slower light than in photonic-crystal waveguides8. Optical pulse delays of 16 ns with a delay-bandwidth product of 0.8 are observed. This implementation of atomic quantum state control in integrated photonic structures will enable coherent photonics at ultralow power levels. Researchers exploit atomic quantum state control in a fully integrated photonic atomic spectroscopy chip to reduce the group velocity of light by a factor of 1,200 — the lowest group velocity ever reported for a solid-state material. The findings will enable the creation of on-chip nonlinear optical devices with enhanced quantum coherence operating at ultralow power levels.
TL;DR: Four-wave mixing is observed in a silicon W1 photonic crystal waveguide and the dispersion dependence of the idler conversion efficiency is measured and shown to be enhanced at wavelengths exhibiting slow group velocities.
Abstract: Four-wave mixing is observed in a silicon W1 photonic crystal waveguide. The dispersion dependence of the idler conversion efficiency is measured and shown to be enhanced at wavelengths exhibiting slow group velocities. A 12-dB increase in the conversion efficiency is observed. Concurrently, a decrease in the conversion bandwidth is observed due to the increase in group velocity dispersion in the slow-light regime. The experimentally observed conversion efficiencies agree with the numerically modeled results.
TL;DR: In this paper, slow-light photonic crystals were used to enhance optical switching and modulation in silicon, and an extinction ratio in excess of 15 dB was obtained over the entire 11nm bandwidth of the modulator.
Abstract: We use slow-light photonic crystals to enhance optical switching and modulation in silicon. By using dispersion-engineered designs, a switch as short as 5 ?m was achieved, in which we have demonstrated rerouting of optical pulses on a 3-ps time scale through the absorption of a femtosecond pulse. We additionally demonstrate a modulator with a Mach-Zehnder interferometer (MZI) configuration with flat-band slow-light photonic crystal phase shifters that is designed to give a large group-index-bandwidth product. An extinction ratio in excess of 15 dB is obtained over the entire 11-nm bandwidth of the modulator.
TL;DR: Experimental results of label-free anti-bovine serum albumin (anti-BSA) antibody detection using a SOI planar photonic crystal waveguide previously bio-functionalized with complementary BSA antigen probes are reported.
Abstract: We report experimental results of label-free anti-bovine serum albumin (anti-BSA) antibody detection using a SOI planar photonic crystal waveguide previously bio-functionalized with complementary BSA antigen probes. Sharp fringes appearing in the slow-light regime near the edge of the guided band are used to perform the sensing. We have modeled the presence of these band edge fringes and demonstrated the possibility of using them for sensing purposes by performing refractive index variations detection, achieving a sensitivity of 174.8 nm/RIU. Then, label-free anti-BSA biosensing experiments have been carried out, estimating a surface mass density detection limit below 2.1 pg/mm2 and a total mass detection limit below 0.2 fg.
TL;DR: This work demonstrates for the first time a continuously tunable 360 degrees microwave phase shifter spanning a microwave bandwidth of several tens of GHz (up to 40 GHz), exploiting the phenomenon of coherent population oscillations in combination with a regeneration stage realized by four-wave mixing effects.
Abstract: In this work we demonstrate for the first time, to the best of our knowledge, a continuously tunable 360° microwave phase shifter spanning a microwave bandwidth of several tens of GHz (up to 40 GHz) by slow light effects. The proposed device exploits the phenomenon of coherent population oscillations, enhanced by optical filtering, in combination with a regeneration stage realized by four-wave mixing effects. This combination provides scalability: three hybrid stages are demonstrated but the technology allows an all-integrated device. The microwave operation frequency limitations of the suggested technique, dictated by the underlying physics, are also analyzed.
TL;DR: A novel type of slow light photonic crystal waveguide which can produce unusual "U" type group index - frequency curves with constant group index n(g) over large bandwidth is demonstrated.
Abstract: We demonstrate a novel type of slow light photonic crystal waveguide which can produce unusual “U” type group index - frequency curves with constant group index ng over large bandwidth. By shifting the boundaries of this waveguide, flexible control of ng (10
TL;DR: In this article, a light pulse propagating through a Si-based photonic-crystal waveguide is adiabatically blueshifted when the refractive index of the Si is reduced on a femtosecond time scale.
Abstract: We demonstrate by experiment and theory that a light pulse propagating through a Si-based photonic-crystal waveguide is adiabatically blueshifted when the refractive index of the Si is reduced on a femtosecond time scale. Thanks to the use of slow-light modes, we are able to shift a 1.3-ps pulse at telecom frequencies by 0.3 THz with an efficiency as high as 80% in a waveguide as short as 19 µm. An analytic theory reproduces the experimental data excellently, which shows that adiabatic dynamics are possible even on the femtosecond time scale as long as the external stimulus conserves the spatial symmetry of the system.
TL;DR: Coupled-ring resonator-based slow light structures are reported and discussed by combining the advantages of high index contrast silicon-on-insulator technology with an efficient thermo-optical activation as mentioned in this paper.
Abstract: Coupled-ring resonator-based slow light structures are reported and discussed By combining the advantages of high index contrast silicon-on-insulator technology with an efficient thermo-optical activation, they provide an on-chip solution with a bandwidth of up to 100 GHz and a slowdown factor of up to 16, as well as a continuous reconfiguration scheme and a fine tunability The performance of these devices is investigated in detail for both static and dynamic operation, in order to evaluate their potential in optical signal processing applications at high bit rate The main impairments imposed by fabrication imperfections are also discussed in relation to the slowdown factor In particular, the analysis of the impact of backscatter, disorder and two-photon absorption on the device transfer function reveals the ultimate limits of these structures and provides valuable design rules for their optimization
TL;DR: In this paper, it was shown that the incorporation of thin layers made of an active medium adjacently to the core layer of a negative-refractive-index waveguide can completely remove dissipative losses in a slow-light regime where the effective index of the guided wave is negative.
Abstract: We review recent theoretical and experimental breakthroughs in the realm of slow and stopped light in structured photonic media featuring negative electromagnetic parameters (permittivity/permeability and/or refractive index). We explain how and why these structures can enable complete stopping of light even in the presence of disorder and, simultaneously, dissipative losses. Using full-wave numerical simulations we show that the incorporation of thin layers made of an active medium adjacently to the core layer of a negative-refractive-index waveguide can completely remove dissipative losses – in a slow-light regime where the effective index of the guided wave is negative.
TL;DR: In this paper, the authors demonstrate state-of-the-art slow light in silicon-on-insulator photonic crystal coupled waveguide, which allows slow light pulse transmission and its tunable delay by means of structural chirping.
Abstract: In this paper, we demonstrate state-of-the-art slow light in silicon-on-insulator photonic crystal coupled waveguide, which allows slow light pulse transmission and its tunable delay by means of structural chirping. The key idea of this study is the application of a folded chirping profile to the structure, instead of the conventional monotonous chirping. It suppresses unwanted spectral oscillation caused by structural disordering and expands the tuning range. By postprocessing an airhole-diameter-chirped device, we show that 0.9-ps-wide slow light pulses are delayed for 72 ps, corresponding to a buffering capacity of 80 bits. In a separate, unchirped device, we demonstrate a tunable delay by applying thermally induced index chirping. Here, a maximum tuning range of 103 ps and a tunable capacity of 22 bits are obtained.
TL;DR: Using Fourier optics, it is shown that quasi-phase matching between the third-harmonic signal and the fundamental mode is provided in this geometry by coupling to the continuum of radiation modes above the light line.
Abstract: Using Fourier optics, we retrieve the wavevector dependence of the third-harmonic (green) light generated in a slow light silicon photonic crystal waveguide. We show that quasi-phase matching between the third-harmonic signal and the fundamental mode is provided in this geometry by coupling to the continuum of radiation modes above the light line. This process sustains third-harmonic generation with a relatively high efficiency and a substantial bandwidth limited only by the slow light window of the fundamental mode. The results give us insights into the physics of this nonlinear process in the presence of strong absorption and dispersion at visible wavelengths where bandstructure calculations are problematic. Since the characteristics (e.g. angular pattern) of the third-harmonic light primarily depend on the fundamental mode dispersion, they could be readily engineered.
TL;DR: In this article, four-wave mixing is observed in a silicon W1 photonic crystal waveguide and the dispersion dependence of the idler conversion efficiency is measured and shown to be enhanced at wavelengths exhibiting slow group velocity.
Abstract: Four-wave mixing is observed in a silicon W1 photonic crystal waveguide. The dispersion dependence of the idler conversion efficiency is measured and shown to be enhanced at wavelengths exhibiting slow group velocities. A 12-dB increase in the conversion efficiency is observed. Concurrently, a decrease in the conversion bandwidth is observed due to the increase in group velocity dispersion in the slow-light regime. The experimentally observed conversion efficiencies agree with the numerically modeled results.
TL;DR: The apparent trade-off relationship between group index and bandwidth is revealed systematically and it is shown that as the radius of the innermost hole is increased above a certain value, the former one decreases and the latter one increases both exponentially but with a different ratio.
Abstract: We investigate slow light propagation in monomode photonic crystal waveguides with different spectral features such as constant group index, high bandwidth and low group velocity dispersion. The form of the waveguide mode alters dramatically and spans three different spectral intervals by tuning the size of the boundary holes. Namely, slope of the band gap guided mode changes sign from negative to positive toward the Brillouin zone edge. In between there is a transition region where modes have nearly zero slopes. Maximum group index occurs at these turning points at the expense of high dispersion and narrow bandwidth. The apparent trade-off relationship between group index and bandwidth is revealed systematically. We show that as the radius of the innermost hole is increased above a certain value, the former one decreases and the latter one increases both exponentially but with a different ratio. The product of average group index and bandwidth is defined as a figure of merit which reaches up to a value of approximately 0.30 after a detailed parametric search. The findings of the frequency domain analysis obtained by plane wave expansion method are confirmed via finite-difference time-domain study.