Yanhua Hong - Academia.edu (original) (raw)
Papers by Yanhua Hong
Photonics, 2022
In this paper, microwave photonic signal generation based on the period-one dynamic of optically ... more In this paper, microwave photonic signal generation based on the period-one dynamic of optically injected discrete mode (DM) semiconductor lasers has been experimentally demonstrated and numerically simulated. The results show that the frequency of the generated microwave increases linearly with the frequency detuning or optical injection ratio. In addition, a single optical feedback loop is sufficient to reduce the microwave linewidth without significantly deteriorating side mode suppression. The simulation results using a model considering the nonlinear dependencies of the carrier recombination agree well with the experimental results, which indicates that the nonlinear carrier recombination effect is important in determining the nonlinear dynamics of optically injected DM lasers.
Optics Express, 2021
The chaotic output emitted by a diode laser with optical feedback has fascinated the community fo... more The chaotic output emitted by a diode laser with optical feedback has fascinated the community for decades. The external cavity delay time imparts a weak level of periodicity to the laser output (the so-called "time delay signature", TDS) that is a drawback for applications that require random optical signals. A lot of efforts have focused in suppressing the TDS either by post-processing the signal or by using alternative ways to generate random optical signals. Here, we compare the signals generated by two optical feedback setups: in the first one, the stimulated Brillouin backscattered light from a standard optical fibre is re-injected into the laser (stimulated Brillouin scattering optical feedback, SBSOF); in the second one, the light transmitted through the fibre is re-injected into the laser (conventional optical feedback, COF). We analyse the permutation entropy, a well-known measure of complexity that captures order relations between values of a time series. We fin...
IEEE Photonics Journal, 2021
Matching filter (MF)-free digital filter multiplexed (DFM) single sideband (SSB) OFDM intensity m... more Matching filter (MF)-free digital filter multiplexed (DFM) single sideband (SSB) OFDM intensity modulation and direct detection (IMDD) dual-channel transmissions of 51.25Gbit/s over 25km SSMFs are experimentally demonstrated. It is shown that both transmission system impairments and digital filter characteristic variations can only lead to <1dB transmission performance degradations. Compared with the MF-free DFM-based double sideband (DSB) OFDM technique, the SSB technique has a similar receiver DSP complexity and provides almost twice the maximum signal transmission capacity. When compared with a conventional DFM technique incorporating a dedicated shaping and matching filter pair for each channel, the present SSB technique achieves a 10-fold reduction of receiver DSP complexity and 7.82Gbit/s of additional signal transmission throughput. We demonstrate these throughput and complexity advantages by modelling and measurement.
Optics Express, 2020
Chaos generation in a discrete-mode (DM) laser subject to optical feedback is experimentally expl... more Chaos generation in a discrete-mode (DM) laser subject to optical feedback is experimentally explored. The results show that a DM laser with only optical feedback can produce flat broadband chaos under an optimized feedback ratio. The effect of the laser bias current on the bandwidth and flatness of chaos is also investigated. It shows that the higher bias current, the better the flatness that can be obtained at the optimal feedback ratio.
Sensors, 2021
A novel transmission technique—namely, a DFT-spread spectrally overlapped hybrid OFDM–digital fil... more A novel transmission technique—namely, a DFT-spread spectrally overlapped hybrid OFDM–digital filter multiple access (DFMA) PON based on intensity modulation and direct detection (IMDD)—is here proposed by employing the discrete Fourier transform (DFT)-spread technique in each optical network unit (ONU) and the optical line terminal (OLT). Detailed numerical simulations are carried out to identify optimal ONU transceiver parameters and explore their maximum achievable upstream transmission performances on the IMDD PON systems. The results show that the DFT-spread technique in the proposed PON is effective in enhancing the upstream transmission performance to its maximum potential, whilst still maintaining all of the salient features associated with previously reported PONs. Compared with previously reported PONs excluding DFT-spread, a significant peak-to-average power ratio (PAPR) reduction of over 2 dB is achieved, leading to a 1 dB reduction in the optimal signal clipping ratio (...
IEEE Photonics Technology Letters, 2021
Two new dynamic-state switching phenomena are experimentally observed in a vertical-cavity surfac... more Two new dynamic-state switching phenomena are experimentally observed in a vertical-cavity surface-emitting laser with polarization-preserved external-cavity optical feedback. One is switching between a steady state and a quasi-periodic state, and the other is switching between two different steady states. Both switching phenomena occur in the same polarization and the switching period is equal to the round-trip time in the external feedback cavity. The evolution of the two switching phenomena is experimentally investigated in detail. This work not only enriches the understanding of laser nonlinear dynamics but also provides an all-optical alternative for generation of special signals for possible applications.
IEEE Photonics Technology Letters, 2018
IEEE Journal of Quantum Electronics, 2016
The time-delay signature and chaos bandwidth in three-cascaded vertical-cavity surface-emitting l... more The time-delay signature and chaos bandwidth in three-cascaded vertical-cavity surface-emitting lasers (VCSELs) has been investigated experimentally. A peak value of autocorrelation coefficient at the feedback round trip time and the ratio between this peak value and its background are used to quantitatively identify the time-delay (TD) signature of chaos. A new conceptpeak to side-peak ratio is introduced for better quantification of the TD signature concealment. The peak to side-peak ratio is defined as the ratio between the peak value of autocorrelation coefficient at the TD and the peak value at a delay time other than the TD and zero delay time. Three injection cases, small bandwidth, intermediate bandwidth and wide bandwidth of the injecting chaos signals, have been used to study the effect of the bandwidth of the injecting chaos on the TD concealment. The experimental results show that the time-delay signature can be totally concealed in the slave laser subject to the intermediate bandwidth of chaotic optical injection over a wide frequency detuning range.
Optical Engineering, 2018
Three-dimensional measurement of small-object surfaces on the basis of fiber Three-dimensional me... more Three-dimensional measurement of small-object surfaces on the basis of fiber Three-dimensional measurement of small-object surfaces on the basis of fiber optic interferometric fringe projection optic interferometric fringe projection
Journal of the Optical Society of America B, 2020
Characteristics of microwave photonic signal generation based on the period-one dynamic in an opt... more Characteristics of microwave photonic signal generation based on the period-one dynamic in an optically injected vertical-cavity surface-emitting laser are studied systematically. The evolutions of the linewidth, power, and second-harmonic ratio of the generated microwave are investigated as a function of injection strength and frequency detuning. The effect of optical feedback on the linewidth and the phase noise of the generated microwave photonic signal is also studied in detail. With the help of optical feedback, the linewidth can be effectively reduced by increasing the feedback strength and feedback delay time. However, there is an optimal feedback delay time to minimize the phase noise.
IEEE Journal of Quantum Electronics, 2019
Dynamics of a multimode quantum dot laser with polarization-rotated optical feedback is investiga... more Dynamics of a multimode quantum dot laser with polarization-rotated optical feedback is investigated in a wide range of bias current. The results reveal that the laser is more sensitive to optical feedback when the polarization of feedback beam is rotated a large angle from the original polarization, which is different from the results in DFB lasers. Anticorrelated fluctuations between orthogonal polarizations are observed in a certain range of selected polarizations. Accordingly, dynamics in the total power can be weaker than that in a selected polarization. The anticorrelated polarization dynamics may be related to different polarizations of longitudinal modes. Index Terms-Optical feedback, polarization, quantum dot lasers I. INTRODUCTION SING multiple layers of nanostructures as active medium, quantum dot lasers (QDLs) have advantages over bulk and quantum-well counterparts in many respects such as threshold current, temperature stability, and beam quality [1]-[3]. These advantages make quantum dot lasers promising optical transmitters for data communications, especially in short-reach communication links. Because of finite intraband relaxation time, a QDL can exhibit excited-state (ES) transition in addition to ground-state (GS) transition [4]. These two emissions can occur exclusively or simultaneously. Accordingly, a QDL can emit two wavelengths that differs several tens of nanometers, thus being possible for terahertz applications. It is well known that bulk and quantum-well semiconductor lasers are sensitive to optical feedback.
IEEE Journal of Quantum Electronics, 2019
IEEE Journal of Quantum Electronics, 2019
We experimentally demonstrate high-speed correlated random bit generation in real time using sync... more We experimentally demonstrate high-speed correlated random bit generation in real time using synchronized chaotic lasers commonly driven by a laser with dispersive feedback. The dispersive feedback from a chirped fiber Bragg grating induces frequency-dependent feedback delay and thus no longer causes time-delay signature, and resultantly ensures the signal randomness and security of chaotic laser. Driven by the time-delay signature-free chaotic signal, the two response lasers are routed into chaotic states and establish a synchronization with correlation beyond 0.97 while they maintain a low correlation level with the drive signal. Through quantizing the synchronized laser chaos with a one-bit differential comparator, real-time 2.5-Gb/s correlated random bits with verified randomness are experimentally obtained with a bit error ratio of 0.07. Combining with a robust sampling method, the BER could be further decreased to 1×10 −4 corresponding to an effective generation rate of 1.7 Gb/s. Bit error analysis indicates that the bit error ratio between the responses is lower than that between the drive and responses over a wide parameter region due to the synchronization superiority of the responses over the drive.
IEEE Journal of Selected Topics in Quantum Electronics, 2019
IET Optoelectronics, 2018
In this paper, we propose a novel technique for generating ultrashort pulses using a semiconducto... more In this paper, we propose a novel technique for generating ultrashort pulses using a semiconductor laser subject to strong optical feedback from short external cavities. The influence of three system parameters, viz the external cavity length, the injection current and the feedback strength on the characteristics of the ultrashort pulses are numerically investigated. The results show that the pulse width decreases and the pulse peak increases with increase of any of these three parameters. The repetition frequency of the ultrashort pulses decreases with increase of the feedback strength but increases with increase of the injection current. Based on these results, ultrashort pulses with a pulse width of 3.6 ps and a repetition frequency of 2.3 GHz have been achieved when the injection current is four times the threshold current. The pulse width can be further decreased and the repetition frequency can be further increased by appropriately adjusting the external cavity length and feedback strength. The results presented in this paper open up a new route for designing ultrashort pulse generators for incorporation in future photonic integrated optical circuits.
Optics Communications, 2016
Time delay (TD) signatures are studied experimentally in orthogonal polarizations and in individu... more Time delay (TD) signatures are studied experimentally in orthogonal polarizations and in individual transverse modes respectively in a VCSEL operating with three transverse modes. Different types of concealment of the TD signatures are observed when the polarization of feedback is rotated through large angles. Effects of feedback strength and external cavity length on the TD signatures are investigated. Weak feedback leads to better concealment of the TD signatures in the dominant polarization. When the roundtrip time difference between the two external cavities is close to a half of the relaxation oscillation period, the TD signatures are minimized.
Optics Express, 2017
Photonic microwave generation based on period-one dynamics of an optically injected VCSEL has bee... more Photonic microwave generation based on period-one dynamics of an optically injected VCSEL has been study experimentally. The results have shown that the frequency of the generated microwave signal can be broadly tunable through the adjustment of the injection power and the frequency detuning. Strong optical injection power and higher frequency detuning are favorable for obtaining a high frequency microwave signal. These results are similar to those found in systems based on distributed feedback lasers and quantum dot lasers. The variation of the microwave power at the fundamental frequency and the second-harmonic distortion have also been characterized.
IEEE Journal of Selected Topics in Quantum Electronics, 2017
The effect of bias current on the complexity and time-delay signature of chaotic signals in semic... more The effect of bias current on the complexity and time-delay signature of chaotic signals in semiconductor lasers with polarization preserved optical feedback has been studied experimentally and theoretically. The peak value of the autocorrelation coefficient and the normalized permutation entropy at the feedback round trip time are used to quantify the time delay signature and complexity, respectively. The results show that the time-delay signature is approximately in an inverse relationship with the complexity of chaos when the semiconductor laser is subject to low or strong optical feedback. However, the inverse relationship disappears when the laser operates at higher bias currents with intermediate feedback strength. The simulation results are qualitatively agreed with the experimental results.
Photonics, 2022
In this paper, microwave photonic signal generation based on the period-one dynamic of optically ... more In this paper, microwave photonic signal generation based on the period-one dynamic of optically injected discrete mode (DM) semiconductor lasers has been experimentally demonstrated and numerically simulated. The results show that the frequency of the generated microwave increases linearly with the frequency detuning or optical injection ratio. In addition, a single optical feedback loop is sufficient to reduce the microwave linewidth without significantly deteriorating side mode suppression. The simulation results using a model considering the nonlinear dependencies of the carrier recombination agree well with the experimental results, which indicates that the nonlinear carrier recombination effect is important in determining the nonlinear dynamics of optically injected DM lasers.
Optics Express, 2021
The chaotic output emitted by a diode laser with optical feedback has fascinated the community fo... more The chaotic output emitted by a diode laser with optical feedback has fascinated the community for decades. The external cavity delay time imparts a weak level of periodicity to the laser output (the so-called "time delay signature", TDS) that is a drawback for applications that require random optical signals. A lot of efforts have focused in suppressing the TDS either by post-processing the signal or by using alternative ways to generate random optical signals. Here, we compare the signals generated by two optical feedback setups: in the first one, the stimulated Brillouin backscattered light from a standard optical fibre is re-injected into the laser (stimulated Brillouin scattering optical feedback, SBSOF); in the second one, the light transmitted through the fibre is re-injected into the laser (conventional optical feedback, COF). We analyse the permutation entropy, a well-known measure of complexity that captures order relations between values of a time series. We fin...
IEEE Photonics Journal, 2021
Matching filter (MF)-free digital filter multiplexed (DFM) single sideband (SSB) OFDM intensity m... more Matching filter (MF)-free digital filter multiplexed (DFM) single sideband (SSB) OFDM intensity modulation and direct detection (IMDD) dual-channel transmissions of 51.25Gbit/s over 25km SSMFs are experimentally demonstrated. It is shown that both transmission system impairments and digital filter characteristic variations can only lead to <1dB transmission performance degradations. Compared with the MF-free DFM-based double sideband (DSB) OFDM technique, the SSB technique has a similar receiver DSP complexity and provides almost twice the maximum signal transmission capacity. When compared with a conventional DFM technique incorporating a dedicated shaping and matching filter pair for each channel, the present SSB technique achieves a 10-fold reduction of receiver DSP complexity and 7.82Gbit/s of additional signal transmission throughput. We demonstrate these throughput and complexity advantages by modelling and measurement.
Optics Express, 2020
Chaos generation in a discrete-mode (DM) laser subject to optical feedback is experimentally expl... more Chaos generation in a discrete-mode (DM) laser subject to optical feedback is experimentally explored. The results show that a DM laser with only optical feedback can produce flat broadband chaos under an optimized feedback ratio. The effect of the laser bias current on the bandwidth and flatness of chaos is also investigated. It shows that the higher bias current, the better the flatness that can be obtained at the optimal feedback ratio.
Sensors, 2021
A novel transmission technique—namely, a DFT-spread spectrally overlapped hybrid OFDM–digital fil... more A novel transmission technique—namely, a DFT-spread spectrally overlapped hybrid OFDM–digital filter multiple access (DFMA) PON based on intensity modulation and direct detection (IMDD)—is here proposed by employing the discrete Fourier transform (DFT)-spread technique in each optical network unit (ONU) and the optical line terminal (OLT). Detailed numerical simulations are carried out to identify optimal ONU transceiver parameters and explore their maximum achievable upstream transmission performances on the IMDD PON systems. The results show that the DFT-spread technique in the proposed PON is effective in enhancing the upstream transmission performance to its maximum potential, whilst still maintaining all of the salient features associated with previously reported PONs. Compared with previously reported PONs excluding DFT-spread, a significant peak-to-average power ratio (PAPR) reduction of over 2 dB is achieved, leading to a 1 dB reduction in the optimal signal clipping ratio (...
IEEE Photonics Technology Letters, 2021
Two new dynamic-state switching phenomena are experimentally observed in a vertical-cavity surfac... more Two new dynamic-state switching phenomena are experimentally observed in a vertical-cavity surface-emitting laser with polarization-preserved external-cavity optical feedback. One is switching between a steady state and a quasi-periodic state, and the other is switching between two different steady states. Both switching phenomena occur in the same polarization and the switching period is equal to the round-trip time in the external feedback cavity. The evolution of the two switching phenomena is experimentally investigated in detail. This work not only enriches the understanding of laser nonlinear dynamics but also provides an all-optical alternative for generation of special signals for possible applications.
IEEE Photonics Technology Letters, 2018
IEEE Journal of Quantum Electronics, 2016
The time-delay signature and chaos bandwidth in three-cascaded vertical-cavity surface-emitting l... more The time-delay signature and chaos bandwidth in three-cascaded vertical-cavity surface-emitting lasers (VCSELs) has been investigated experimentally. A peak value of autocorrelation coefficient at the feedback round trip time and the ratio between this peak value and its background are used to quantitatively identify the time-delay (TD) signature of chaos. A new conceptpeak to side-peak ratio is introduced for better quantification of the TD signature concealment. The peak to side-peak ratio is defined as the ratio between the peak value of autocorrelation coefficient at the TD and the peak value at a delay time other than the TD and zero delay time. Three injection cases, small bandwidth, intermediate bandwidth and wide bandwidth of the injecting chaos signals, have been used to study the effect of the bandwidth of the injecting chaos on the TD concealment. The experimental results show that the time-delay signature can be totally concealed in the slave laser subject to the intermediate bandwidth of chaotic optical injection over a wide frequency detuning range.
Optical Engineering, 2018
Three-dimensional measurement of small-object surfaces on the basis of fiber Three-dimensional me... more Three-dimensional measurement of small-object surfaces on the basis of fiber Three-dimensional measurement of small-object surfaces on the basis of fiber optic interferometric fringe projection optic interferometric fringe projection
Journal of the Optical Society of America B, 2020
Characteristics of microwave photonic signal generation based on the period-one dynamic in an opt... more Characteristics of microwave photonic signal generation based on the period-one dynamic in an optically injected vertical-cavity surface-emitting laser are studied systematically. The evolutions of the linewidth, power, and second-harmonic ratio of the generated microwave are investigated as a function of injection strength and frequency detuning. The effect of optical feedback on the linewidth and the phase noise of the generated microwave photonic signal is also studied in detail. With the help of optical feedback, the linewidth can be effectively reduced by increasing the feedback strength and feedback delay time. However, there is an optimal feedback delay time to minimize the phase noise.
IEEE Journal of Quantum Electronics, 2019
Dynamics of a multimode quantum dot laser with polarization-rotated optical feedback is investiga... more Dynamics of a multimode quantum dot laser with polarization-rotated optical feedback is investigated in a wide range of bias current. The results reveal that the laser is more sensitive to optical feedback when the polarization of feedback beam is rotated a large angle from the original polarization, which is different from the results in DFB lasers. Anticorrelated fluctuations between orthogonal polarizations are observed in a certain range of selected polarizations. Accordingly, dynamics in the total power can be weaker than that in a selected polarization. The anticorrelated polarization dynamics may be related to different polarizations of longitudinal modes. Index Terms-Optical feedback, polarization, quantum dot lasers I. INTRODUCTION SING multiple layers of nanostructures as active medium, quantum dot lasers (QDLs) have advantages over bulk and quantum-well counterparts in many respects such as threshold current, temperature stability, and beam quality [1]-[3]. These advantages make quantum dot lasers promising optical transmitters for data communications, especially in short-reach communication links. Because of finite intraband relaxation time, a QDL can exhibit excited-state (ES) transition in addition to ground-state (GS) transition [4]. These two emissions can occur exclusively or simultaneously. Accordingly, a QDL can emit two wavelengths that differs several tens of nanometers, thus being possible for terahertz applications. It is well known that bulk and quantum-well semiconductor lasers are sensitive to optical feedback.
IEEE Journal of Quantum Electronics, 2019
IEEE Journal of Quantum Electronics, 2019
We experimentally demonstrate high-speed correlated random bit generation in real time using sync... more We experimentally demonstrate high-speed correlated random bit generation in real time using synchronized chaotic lasers commonly driven by a laser with dispersive feedback. The dispersive feedback from a chirped fiber Bragg grating induces frequency-dependent feedback delay and thus no longer causes time-delay signature, and resultantly ensures the signal randomness and security of chaotic laser. Driven by the time-delay signature-free chaotic signal, the two response lasers are routed into chaotic states and establish a synchronization with correlation beyond 0.97 while they maintain a low correlation level with the drive signal. Through quantizing the synchronized laser chaos with a one-bit differential comparator, real-time 2.5-Gb/s correlated random bits with verified randomness are experimentally obtained with a bit error ratio of 0.07. Combining with a robust sampling method, the BER could be further decreased to 1×10 −4 corresponding to an effective generation rate of 1.7 Gb/s. Bit error analysis indicates that the bit error ratio between the responses is lower than that between the drive and responses over a wide parameter region due to the synchronization superiority of the responses over the drive.
IEEE Journal of Selected Topics in Quantum Electronics, 2019
IET Optoelectronics, 2018
In this paper, we propose a novel technique for generating ultrashort pulses using a semiconducto... more In this paper, we propose a novel technique for generating ultrashort pulses using a semiconductor laser subject to strong optical feedback from short external cavities. The influence of three system parameters, viz the external cavity length, the injection current and the feedback strength on the characteristics of the ultrashort pulses are numerically investigated. The results show that the pulse width decreases and the pulse peak increases with increase of any of these three parameters. The repetition frequency of the ultrashort pulses decreases with increase of the feedback strength but increases with increase of the injection current. Based on these results, ultrashort pulses with a pulse width of 3.6 ps and a repetition frequency of 2.3 GHz have been achieved when the injection current is four times the threshold current. The pulse width can be further decreased and the repetition frequency can be further increased by appropriately adjusting the external cavity length and feedback strength. The results presented in this paper open up a new route for designing ultrashort pulse generators for incorporation in future photonic integrated optical circuits.
Optics Communications, 2016
Time delay (TD) signatures are studied experimentally in orthogonal polarizations and in individu... more Time delay (TD) signatures are studied experimentally in orthogonal polarizations and in individual transverse modes respectively in a VCSEL operating with three transverse modes. Different types of concealment of the TD signatures are observed when the polarization of feedback is rotated through large angles. Effects of feedback strength and external cavity length on the TD signatures are investigated. Weak feedback leads to better concealment of the TD signatures in the dominant polarization. When the roundtrip time difference between the two external cavities is close to a half of the relaxation oscillation period, the TD signatures are minimized.
Optics Express, 2017
Photonic microwave generation based on period-one dynamics of an optically injected VCSEL has bee... more Photonic microwave generation based on period-one dynamics of an optically injected VCSEL has been study experimentally. The results have shown that the frequency of the generated microwave signal can be broadly tunable through the adjustment of the injection power and the frequency detuning. Strong optical injection power and higher frequency detuning are favorable for obtaining a high frequency microwave signal. These results are similar to those found in systems based on distributed feedback lasers and quantum dot lasers. The variation of the microwave power at the fundamental frequency and the second-harmonic distortion have also been characterized.
IEEE Journal of Selected Topics in Quantum Electronics, 2017
The effect of bias current on the complexity and time-delay signature of chaotic signals in semic... more The effect of bias current on the complexity and time-delay signature of chaotic signals in semiconductor lasers with polarization preserved optical feedback has been studied experimentally and theoretically. The peak value of the autocorrelation coefficient and the normalized permutation entropy at the feedback round trip time are used to quantify the time delay signature and complexity, respectively. The results show that the time-delay signature is approximately in an inverse relationship with the complexity of chaos when the semiconductor laser is subject to low or strong optical feedback. However, the inverse relationship disappears when the laser operates at higher bias currents with intermediate feedback strength. The simulation results are qualitatively agreed with the experimental results.