Analysis and simulation of strained quantum wells slow light devices according to V-type EIT

This paper represents the influences of temperature and hydrostatic pressure variations on GaAs/AlGaAs multiple quantum well slow light systems based on coherence population oscillations. An analytical model in non-integer dimension space is used to study the considerable effects of these parameters on optical properties of the slow light apparatus. Exciton oscillator strength and fractional dimension constants have special roles on the analytical model in fractional dimension. Hence, the impacts of hydrostatic pressure and temperature on exciton oscillator strength and fractional dimension quantity are investigated theoretically in this paper. Based on the achieved results, temperature and hydrostatic pressure play key roles on optical parameters of the slow light systems, such as the slow down factor and central energy of the device. It is found that the slope and value of the refractive index real part change with alterations of temperature and hydrostatic pressure in the range of 5-40 deg of Kelvin and 1 bar to 2 kbar, respectively. Thus, the peak value of the slow down factor can be adjusted by altering these parameters. Moreover, the central energy of the device shifts when the hydrostatic pressure is applied to the slow light device or temperature is varied. In comparison with previous reported experimental results, our simulations follow them successfully. It is shown that the maximum value of the slow down factor is estimated close to 5.5×104 with a fine adjustment of temperature and hydrostatic pressure. Meanwhile, the central energy shift of the slow light device rises up to 27 meV, which provides an appropriate basis for different optical devices in which multiple quantum well slow light is one of their essential subsections. This multiple quantum well slow light device has potential applications for use as a tunable optical buffer and pressure/temperature sensors.

Inverse design of slow light devices at telecommunication band based on metamaterials using a deep learning attempt

Slow light Transparency window can be achieved with the help of Electromagnetically Induced Transparency (EIT) method and Tunneling Induced Transparency (TIT) method accompanied by observing tunneling effect between InAs quantum dot structure with energy gap of 0.35ev and a thin layer of GaAs potential barrier with energy gap of 1.42ev. By investigating different parameters such as group velocity and Slow Down Factor (SDF) coefficient at different detuning frequencies, we have obtained an improved design in tunneling and identifying some better conditions. Under TIT condition, the SDF parameter has improved to the amount of 3.2 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> .

&lt;sec&gt;The phenomenon of electromagnetically induced transparency (EIT)-like in terahertz (THz) metasurfaces facilitates agile manipulation of electromagnetic wave transmission windows and the deceleration of light, rendering it suitable for applications in modulators, absorbers, slow light devices, and more. Traditional design methodologies focus on the coupling between bright-dark modes and bright-bright modes within the unit cell, leveraging interference cancellation effects to regulate electromagnetic wave transmission. Notably, the periodicity of the array structure also plays a pivotal role in modulating the amplitude and resonance intensity of the transparent window, a phenomenon termed lattice-induced transparency (LIT). In this paper, we introduce a gold nanorod structure and an S-shaped gold split-ring resonator supported on a vanadium dioxide (&lt;inline-formula&gt;&lt;tex-math id="M1"&gt;\begin{document}${\rm{VO}}_{2}$\end{document}&lt;/tex-math&gt;&lt;/inline-formula&gt;) thin film to investigate LIT. Unlike conventional structures that solely consider single bright-bright or bright-dark mode coupling, our proposed structure incorporates both bright-bright and bright-dark modes coupling. Furthermore, the dark mode in our structure is not a conventional multipolar mode but rather a surface lattice resonance (SLR) arising from the coupling between lattice modes and the localized surface plasmon resonance (LSPR) of the structure itself.&lt;/sec&gt;&lt;sec&gt;Through the analysis of simulated transmission spectra for the individual gold nanorod and S-shaped split-ring structures, we observed that the gold nanorod exhibits LSPR at 0.985 THz, whereas the S-shaped split-ring structure demonstrates LSPR and SLR at 0.51 THz and 1.025 THz, respectively. When combined, these structures form transparent windows with transmission rates of 66.03% and 59.4% at 0.643 THz and 1.01 THz due to the interplay of bright-bright and bright-dark modes coupling. Upon examining the electric field distribution in the x-y plane, we found that the electric field energy is predominantly concentrated on the S-shaped split-ring.&lt;/sec&gt;&lt;sec&gt;To gain deeper insights into each resonance mode, we employed multipolar decomposition to quantify resonance scattering energy. Our findings revealed that both transparent windows are predominantly governed by electric dipole scattering energy. Further investigations showed that as the array structure’s period varies from 60 μm to 95 μm, the lattice mode progressively couples into the high frequency transmission valley (1.031 THz), giving rise to a high frequency hybrid mode (HFHM). The &lt;i&gt;Q&lt;/i&gt; value of this mode initially increases and then decreases, peaking at 27 when the period is 84 μm. Similarly, as the period continues to increase, the lattice mode couples into the low frequency resonance valley (0.76 THz), forming a low frequency hybrid mode (LFHM) with a &lt;i&gt;Q&lt;/i&gt; value that reaches a maximum of 51 at 115 μm—approximately an order of magnitude higher than that at a period of 60 μm. Additionally, as the periodicity increases, the near field coupling effect between adjacent units diminishes, leading to the gradual disappearance of the two transparent windows.&lt;/sec&gt;&lt;sec&gt;To achieve active control over these transparent windows, we varied the conductivity of &lt;inline-formula&gt;&lt;tex-math id="M2"&gt;\begin{document}${\rm{VO}}_{2}$\end{document}&lt;/tex-math&gt;&lt;/inline-formula&gt; from 20 S/m to 30000 S/m, resulting in a decrease in the transmission amplitudes of the two transparent windows to 37.58% and 3.39%, respectively. Finally, we investigated the slow light effect of the two transparent windows, comparing the maximum group delay between them, which was found to be 8.1 ps. The terahertz metasurface proposed in this study opens up avenues for the design of dynamically tunable sensing and slow light devices in the future.&lt;/sec&gt;

Metasurfaces emerge as exceptional platforms for achieving classical‐analog electromagnetically induced transparency (EIT). In this study, dual‐band EIT is demonstrated by strategically engineering the coupling between a magnetic toroidal dipole (TD) Mie resonance and two quasi‐bound states in the continuum (QBICs) within all‐dielectric metasurfaces. Through deliberate symmetry breaking in the cuboid unit cell—achieved via off‐center holes or U‐shaped configurations—two BICs, predominantly governed by electric TD and magnetic quadrupole modes, are successfully transformed into QBICs with high quality (Q) factors. These QBICs are then coupled to a low‐Q magnetic TD Mie resonance, resulting in the emergence of dual‐band EIT. The corresponding group delays reach up to 9.51 ps (Q = 7,674) and 5.69 ps (Q = 3,631), respectively, and diverge when the Q‐factors approach infinite. Furthermore, the dual‐band EIT with high Q‐factors is experimentally validated by fabricating a series of silicon metasurfaces and characterizing their transmission spectra. Excellent agreement is found between numerical simulation and experimental measurement. Measurement results reveal that both the resonance wavelengths and Q‐factors of the dual‐band EIT are precisely tuned by adjusting the asymmetry parameters. These findings hold significant promise for applications in multi‐wavelength slow light devices and biosensing.

A metal-perovskite hybrid metamaterial, comprising a gold cross and two gold arcs, is proposed. An electromagnetically induced transparency (EIT) based on bright–bright coupling model leads to a transparent window at 0.75 THz. A multipole scattering theory indicates that the EIT effect is generated by the destructive interference between the electric dipole and the toroidal dipole. By tuning the conductivity of perovskite, the EIT effect is dynamically controlled and shows the modulation depth of 34% at 0.75 THz. Moreover, the theoretical results calculated by the two-particle model are in good agreement with the simulated results. The group delay of the proposed EIT metamaterial can also be dynamically tuned and the maximum value of group delay is 3.53 ps. The sensitivity of the proposed EIT metamaterial is 0.182 THz/RIU. Compared with other sensors, our EIT metamaterial shows excellent sensitivity in the terahertz band. Our work provides a novel method for tunable EIT metamaterials and shows a great practical application value of modulators, slow light devices, and sensors.

A three-dimensional structure device that realizes electromagnetic-induced transparency (EIT) in the terahertz band is designed. We use metamaterials to simulate electromagnetic-induced transparency phenomena, through the design of effective metamaterial unit structures, acquire high transmittance while achieving strong dispersion, reducing the absorption of light waves by the medium in the slow light process. EIT’s frequency response is expressed as a narrowband transparent window formed in a large block peak. There are two coupling methods for metamaterials to achieve EIT: bright-bright mode coupling and bright-dark mode coupling. Obviously, the structures in the bright-mode coupled metamaterial unit can be directly excited by incident waves to form a resonant mode, that is, there are at least two radiating mode resonators, which are generally two-dimensional planar structures such as double strips, double rings, etc. This work breaks through the traditional planar patch structure, connects the two resonant rings with cylinders, and innovatively constructs a three-dimensional metamaterial unit. We successfully achieve EIT in the range of 1.06THz to 1.41THz, at a resonance frequency of 1.26THz, the two narrow-band resonance peaks of EIT are located at 1.22THz and 1.30 THz. Realizing EIT through terahertz metamaterials, thereby realizing slow light effect, have paved the way for the design of slow-light devices to meet the future demand for ultra-fast optical signal processing and promote the development of next-generation communication technologies.

Slow-light mesophotonic waveguides have gained increasing interest in the recent years owing to their potential for time-delay control of optical signals, crucial for all-optical circuitry, as well as EM energy storage and field enhancement which is important for driving a stronger light-matter interaction. Yet, the design of such systems has hitherto been predominantly directed by modal-type of analyses in frequency domain. We discuss here why frequency domain analysis fails for real systems, leading to mistaken predictions for the effective propagation speed of the EM signal. In particular, by utilizing a time-domain analysis we demonstrate a slow-light paradigm waveguide system which contradicts the widespread notion that the group-index is generally a good measure of the light's speed effective slow-down factor within the waveguide. In particular, our counterexample shows that it is entirely possible when two modes are compared that it would be the one with the lower group index to yield effectively the larger light slow-down factor. We analyze the salient characteristics of the modes with the higher light slow-down-factor merit to understand how to enable slow light in practical platforms. Our results suggest that in order for a large group index to practically effect a large slowdown factor it should be accompanied by a large modal index bandwidth. This can occur when both the group velocity and the group-velocity dispersion are simultaneously near-zero.

Polarization-insensitive electromagnetically induced transparency (EIT) based on ultra-thin coupling planar metamaterials has been numerically demonstrated. The height (h) of ultra-thin coupling planar metamaterials can reach to 1/94 &#x03BB;, which is the thinnest height so far. Such ultra-thin EIT metamaterials can reduce the cost of production. When the angles of the incident electromagnetic wave are changed, the EIT metamaterials show polarization-insensitive characteristics. When the height of the EIT metamaterials gradually increases, the group index gradually decreases and the transmission peak value and h/&#x03BB; gradually increase. All of above characteristics make the ultra-thin coupling EIT have potential application in slow light devices. In addition, using the coupling of the top and below layer has proposed a way to obtain ultra-thin metamaterials in the microwave region.

Performance of a slow light modulator using corrugated waveguide operating at band edge is studied in terms of bandwidth and loss. It is shown that the electrical bandwidth of the slow-light modulator can be enhanced compared to non-slow light modulators using the same drive voltage, by decreasing the length of the modulator. Limitations imposed by the slow light structure in terms of loss and optical bandwidth are also investigated for medium slow-down factor values using numerical simulations. The loss and optical bandwidth due to the slow light effect would respectively increase and decrease by increasing the slow-down factor. The loss remains in an acceptable range of 3 dB and the optical bandwidth would be slightly more than 400GHz using a slow-down factor of 3. This analysis could open up a new horizon for the realization of high-speed modulators which are useful for microwave photonics applications in the existing photonic IC Foundries.

A detailed discussion is given for the x-ray rocking curve analysis of semiconductor heterointerfaces and strained quantum wells using x-ray interferometry. It is shown that for a single beteroepitaxial layer sample and a multiple quantum well sample, the heterointerface where the composition changes in both anion and cation sublattices can be studied with a half monolayer sensitivity by analyzing the x-ray rocking curve profile. Such sample systems include GaInAs/InP, InGaSb, GaInP/GaAs, ZnSe/GaAs, etc. A simple kinematical diffraction principle involved in the x-ray analysis is explained. Namely, the relative phase difference between the reflection amplitudes of any two layers depends on the total sum of strain (or mismatch)-thickness products over the intervening layers and interfaces. The x-ray interferometry is also effective in measuring the strain-thickness product of strained quantum wells. Experimental data and analysis results are presented for a series of functional device structures having a strained quantum well. For a more complicated sample structure which involves both a (strained) quantum-effect layer and gained interfaces, it is shown that the x-ray interferometry is only capable of providing the total strain-thickness product over the quantum layer and the surrounding interfaces, but no detailed information about the interface grading can be gained frommore » the rocking curve analysis alone if only one isolated sample is measured. An experimental data of such a sample, 0.3{mu}m-GaAs/100{Angstrom}-GaInP/GaAs(001), is analyzed. 15 refs., 6 figs.« less

The fabrication of long-wavelength optoelectronic devices on GaAs substrates is an attractive method for monolithic integration of optical and electronic devices on a single chip for applications in telecommunications. In this letter we describe our studies of one such scheme using a novel structure for spatially separating a portion of the biaxial compressive stress due to lattice mismatch of the layers from the well layer, and demonstrate its feasibility. High quality pseudomorphic strained InGaAs quantum wells were grown on GaAs substrates by molecular beam epitaxy with a band edge between 1.3 and 1.4 μm at room temperature. Low-temperature photoluminescence spectroscopy as well as polarization-dependent absorption measurements in a waveguide geometry was used to characterize the structures.

Damage introduced from sputtering deposition, electron-beam evaporation, and thermal evaporation were investigated with an InGaAs/GaAs strained quantum well structure. This strained quantum well structure was found to be a more sensitive probe of damage, revealing metallization-induced damage where none was found using comparable lattice-matched quantum wells. The damage was found to vary with deposition method, deposition rates, or even different metal sources used. Noticeable degradation of the photoluminescence of the strained quantum well was observed after a thin layer (∼100 Å) of metal was deposited.

Slowed group velocity of light in GaAs/AlGaAs multiple quantum wells (MQWs) for ultrafast photonic applications is numerically estimated and discussed using a fourth-order Runge-Kutta method through observed electromagnetically-induced transparency (EIT) in a transient regime.

InGaAsP lasers incorporating strained quantum wells have recently shown superior performance in the 1.3 /spl mu/m band. We report both high-power, low RIN lasers and high-speed, low theshold lasers obtained from strained quantum well material. In conclusion, we have demonstrated high-performance 1.3 /spl mu/m lasers obtained from strained quantum well material. Lasers can be optimized for both analog and digital applications.