Researchers have recently revealed that hybrid lead halide perovskites exhibit ferroelectricity, which is often associated with other physical characteristics, such as a large nonlinear optical ...response. In this work, the nonlinear optical properties of single crystal inorganic–organic hybrid perovskite CH3NH3PbBr3 are studied. By exciting the material with a 1044 nm laser, strong two‐photon absorption‐induced photoluminescence in the green spectral region is observed. Using the transmission open‐aperture Z‐scan technique, the values of the two‐photon absorption coefficient are observed to be 8.5 cm GW−1, which is much higher than that of standard two‐photon absorbing materials that are industrially used in nonlinear optical applications, such as lithium niobate (LiNbO3), LiTaO3, KTiOPO4, and KH2PO4. Such a strong two‐photon absorption effect in CH3NH3PbBr3 can be used to modulate the spectral and spatial profiles of laser pulses, as well as to reduce noise, and can be used to strongly control the intensity of incident light. In this study, the superior optical limiting, pulse reshaping, and stabilization properties of CH3NH3PbBr3 are demonstrated, opening new applications for perovskites in nonlinear optics.
The two‐photon absorption properties of CH3NH3PbBr3 are investigated by exciting the material with a 1044 nm laser. Such a strong two‐photon absorption effect can be used to modulate the spectral and spatial profiles of laser pulses. In this study, the superior optical limiting, pulse reshaping, and stabilization properties of CH3NH3PbBr3 are demonstrated.
In recent years, many efforts have been devoted in the study, development and application of Green Photonics and Smart Photonics. This book presents recent advances, both theoretical and ...applications, reflecting the cutting-edge technologies and research achievements within these research fields.
Green Photonics intend to develop photonics technologies that can conserve energy, reduce pollution and create renewable energy. Light emitting diodes (LEDs) and solar cells with the characteristics of sustainable and low energy consumption are addressed in this book. The term of Smart Photonics reflect intelligence of optical and optoelectronic components with high sensitivity, fast response time and/or compact size. The book explores various aspects of smart photonics including fiber sensors, optoelectronic devices and waveguide devices.
The chapters in this edited book are written by researchers who presented quality papers at the 2015 International Symposium of Next-Generation Electronics (ISNE 2015), which was held in Taipei, Taiwan. The ISNE 2015 provided a common forum in the areas of optoelectron devices, photonics, integrated circuits, and microelectronic systems and technologies. The technical program consisted of 5 plenary talks, 23 invited talks and more than 250 contributed oral and poster presentations. After a rigorous review process, the ISNE 2015 technical program committee has selected 10 outstanding presentations and invited the authors to prepare extended chapters for inclusion in this book. Of the 10 chapters, five focus on the subject of green photonics, and the others cover smart photonics.
White light generation by mixing red, green, and blue laser diodes (RGB LDs) was demonstrated with Commission International de l'Eclairage coordinates of (0.2928, 0.2981), a correlated color ...temperature of 8382 K, and a color rendering index of 54.4 to provide a maximal illuminance of 7540 lux. All the white lights generated using RGB LDs were set within the risk group-1 criterion to avoid the blue-light hazard to human eyes. In addition, the RGB-LD mixed white light was diffused using a frosted glass to avoid optical aberration and to improve the performance of the lighting source. In addition, visible light communication (VLC) by using RGB-LD mixed white-light carriers and a point-to-point scheme over 1 m was performed in the directly modulated 16-QAM OFDM data format. In back-to-back transmission, the maximal allowable data rate at 10.8, 10.4, and 8 Gbps was determined for R, G, and B LDs, respectively. Moreover, the RGB-LD mixed white light-based indoor wavelength-division multiplexing (WDM)-VLC system yielded a total allowable transmission data rate of 8.8 Gbps over 0.5 m in free space. Such a high-speed RGB-LD mixed WDM-VLC system without any channel interference can be used to simultaneously provide data transmission and white lighting in an indoor environment.
A GaN blue laser diode (BLD)-based visible-light communication link is demonstrated in a seawater environment to provide 16-quadrature amplitude modulation orthogonal frequency-division multiplexing ...(QAM OFDM) data transmission at 14.8 Gbps over 1.7 m. Lengthening the seawater distance to 10.2 m only decreases the transmission data rate by 4 Gbps, as caused by the frquency response limitation of the used avalanche photodiode. To optimize the QAM-OFDM transmission, the sampling rate of the encoded data is compromised to avoid the aliasing and oversampling effects during the waveform extraction procedure. The sampling rate is optimized to 3-5 times of the encoded data bandwidth for suppressing peak-to-average power ratio. Oversampling not only filters out background noise but also attenuates data amplitude to degrade transmission performance. Without using the multicarrier spectrally filtered OFDM, the 16-QAM OFDM data format only promotes the transmission capacity of BLD up to 7.6 Gbps in seawater. With spectrally filtering out the sidelobes of each OFDM subcarrier, the allowable modulation bandwidth is greatly improved from 1.9 to 2.7 GHz, as the intercarrier interference induced crosstalk between subbands is relieved to improve the SNR of the carried data with a raw data rate of up to 10.8 Gbps.
To enable high-speed underwater wireless optical communication (UWOC) in tap-water and seawater environments over long distances, a 450-nm blue GaN laser diode (LD) directly modulated by pre-leveled ...16-quadrature amplitude modulation (QAM) orthogonal frequency division multiplexing (OFDM) data was employed to implement its maximal transmission capacity of up to 10 Gbps. The proposed UWOC in tap water provided a maximal allowable communication bit rate increase from 5.2 to 12.4 Gbps with the corresponding underwater transmission distance significantly reduced from 10.2 to 1.7 m, exhibiting a bit rate/distance decaying slope of -0.847 Gbps/m. When conducting the same type of UWOC in seawater, light scattering induced by impurities attenuated the blue laser power, thereby degrading the transmission with a slightly higher decay ratio of 0.941 Gbps/m. The blue LD based UWOC enables a 16-QAM OFDM bit rate of up to 7.2 Gbps for transmission in seawater more than 6.8 m.
Visible Light Communication (VLC) technology is an emerging technology using visible light modulation that, in the modern world, will mainly facilitate high-speed internet connectivity. VLC provides ...tremendous advantages compared to conventional radio frequency, such as a higher transmission rate, high bandwidth, low-power consumption, no health hazards, less interference, etc., which make it more prominent in recent days. Due to their outstanding features, including low cost, low power consumption, etc., µ-light-emitting diodes (LEDs) have gained considerable attention for VLC implementation, but mostly for the ability to be used for lighting as well as communications. In this review paper, we will focus mainly on recent developments in VLC applications and various factors affecting the modulation bandwidth of VLC devices. Numerous factors, such as quantum confined stark effect (QCSE), carrier lifetime, carrier recombination time, crystal orientation, etc. affect the modulation bandwidth of LEDs, and more information will be discussed in the following sections. This paper will focus on VLC applications based on LEDs but mainly on semipolar μ-LEDs and μ-LED-based arrays with high bandwidths. Another important application of VLC is underwater optical wireless communication (UOWC), which has drawn a huge interest in marine exploration and underwater connectivity, but still faces some challenges because visible light is being used. In addition, this paper will focus on how the current VLC system modulation bandwidth can be enhanced. Many methods have been introduced, such as decreasing the active layer thickness or effective active area or using doping, but the bandwidth is restricted by the recombination time when the system configuration reaches its limit. Therefore, it is important to find alternative ways such as optimizing the system, using the blue filter or using the equalization technology, which will be addressed later. Overall, this review paper provides a brief overview of the VLC-based system performance and some of its potential prospects.
By employing a dual-wavelength (2-λ) vertical cavity surface emitting laser (VCSEL) directly encoded by novel quadrature amplitude modulation generalized frequency division multiplexing (QAM-GFDM) ...modulation schemes with optimized data capacity, a 28-GHz millimeter-wave-over-fiber (MMWoF) link is created for fusing the long-reach single-mode-fiber wired network and the beyond fifth generation (B5G) mobile wireless network without using any localized synthesizer and mixer at the remote receiver end. Detuning the k subcarrier to 2 optimizes the electrical-to-electrical 5-GHz 64-QAM-GFDM link with an error vector magnitude (EVM) of 3.04%, a signal-to-noise ratio (SNR) of 30.3 dB and a bit error ratio (BER) of 2.1×10 -13 . By using this condition to perform the long-reach 50-km optical transmission, the 5-GHz 64-QAM GFDM carried by the 2-λ VCSEL exhibits an SNR of 23.8 dB, an EVM of 6.47% and a BER of 2.2×10 -4 . By fixing the optimized k subcarriers, the maximal bandwidth and raw data rate of the 64-QAM-GFDM transmission can be achieved to 6.75 GHz and 40 Gbit/s, respectively. For the wireless transmission at the remote end, the photo-mixed MMW carrier at 28-GHz exhibits a peak power of -11.4 dBm and a carrier-to-noise ratio (CNR) of 45 dB. After performing the self-heterodyne down-conversion via power envelope detection, the receiving data amplitude is improved from 26.2 to 132 mV with adding a 3-dB attenuator for impedance matching. Under the 2-m wireless transmission via horn antenna pair, the maximal bandwidth and data rate of the received 4-QAM GFDM data respectively achieve 2 GHz and 4 Gbit/s.
Violet laser diode (VLD) based ultrahigh-speed free-space optical (FSO) system is demonstrated for point-to-point data transmission. By directly encoding the VLD with 64-quadrature amplitude ...modulation discrete multi-tone (64-QAM DMT) data stream for optical wireless communication through 0.5-10 m in free space, the point-to-point VLD-based FSO link allows delivering the 64-QAM DMT data at an ultrahigh bit rate of up to 26.4 Gbps. After receiving with a high-speed p-i-n photodiode, such a VLD-FSO link can provide clear constellation plot with error vector magnitude (EVM) of 8.57%, signal-to-noise ratio (SNR) of 21.34 dB and bit error ratio (BER) of 3.17 × 10
under forward-error-correction criterion. The EVM increases from 8.8% to 9.4% and the SNR decreases from 21.1 to 20.6 dB to slightly degrade the reachable data rate from 25.8 to 24 Gbit/s with transmission distance lengthening from 3 to 10 m.
To realize the superiority of data transmission with reduced modal dispersion in OM4- and OM5-mulitmode fiber (MMF), a single transverse mode (SM) vertical cavity surface emitting laser (VCSEL), ...directly encoded with large-capacity data formats for transmissions in OM5-MMF and OM4-MMF, are compared. The SM-VCSEL contains a 12-μm mesa formed by double-oxidized AlGaAs layers, which confines a current-flow area within an aperture of 3 μm. The SM-VCSEL is lasing with a carrier-to-noise ratio of 34.4 dB and a linewidth of 0.05 nm. The SM-VCSEL is biased at 10Ith to provide a modulation bandwidth of 21.4 GHz and a relative intensity noise of -138 dBc/Hz. By encoding the SM-VCSEL with four-level pulse amplitude modulation (PAM-4) at 64 Gbit/s, the bit error ratio (BER) of 32-GBaud PAM-4 data is improved from 7.9 × 10 -5 to 4.9 × 10 -5 under a KP4-FEC criterion by replacing OM4-MMF with OM5-MMF. After OM5-MMF transmission, a bathtub BER plot shows bottom-eye, middle-eye, and top-eye jitter tolerances of 9.3, 10.6, and 7.1 ps, which are much wider than 6.9, 10.1, and 6.5 ps for OM4-MMF, respectively. When encoding the 16-QAM OFDM at 100 Gbit/s, OM5-MMF allows data transmission at 96-Gbit/s with a corresponding error vector magnitude, signal-to-noise ratio, and BER of 16.7%, 15.4 dB, and 3.6 × 10 -3 under preleveling at a slope of 0.3 dB/GHz. Because of the high effective modal bandwidth and low modal dispersion of the OM5-MMF, a relatively low receiving power penalty of 0.1 dB between 100-m and back-to-back (BtB) transmissions is obtained with either the pre-emphasized PAM-4 or the preleveled QAM-OFDM data format. By contrast, the receiving power penalty is 1.04 dB between 100 m and BtB cases during OM4-MMF transmission.
Visible light communication is an emerging high-speed optical wireless communication technology that can be a candidate to alleviate pressure on conventional radio frequency-based technology. In this ...paper, for the first time, the advanced modulation format of probabilistic shaping (PS) bit loading is investigated in a high data rate visible light communication system based on a 450-nm Gallium Nitride laser diode. The characteristic of the system is discussed and PS bit loading discrete multi-tone modulation helps to raise the spectral efficiency and improve the system performance. Higher entropy can be achieved in the same signal-to-noise ratio (SNR) and modulation bandwidth limitation, comparing to bit and power loading. With PS bit loading, an available information rate (AIR) of 10.23 Gbps is successfully achieved at the signal bandwidth of 1.5 GHz in a 1.2 m free space transmission with normalized generalized mutual information above 0.92. And higher AIR can be anticipated with an entropy-loading strategy that fixes the channel characteristic. Experimental results validate that a PS bit loading scheme has the potential to increase the system capacity.
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