Single-mode InGaAsP/InP BH lasers based on high-order slotted surface gratings.

A single-mode InGaAsP/InP buried heterostructure (BH) laser based on high-order slotted surface gratings has been fabricated. The introduction of surface slotted grating can simplify the fabrication process of single-mode BH lasers notably. The laser shows a good single-mode emission performance, with larger than 30 dB side-mode suppression ratio (SMSR) when the current is between 200 and 400 mA. Calculations show that the gain coupling mechanism plays a key role for the slot grating to select the emission wavelength. The linewidth of the laser is measured. The fitted Gaussian and Lorentzian linewidths are 1500 and 550 kHz, respectively.

100-GHz ultra-short high-peak-power colliding-pulse mode-locked laser with asymmetric coating.

By using colliding-pulse mode-locking (CPM) configuration with asymmetric cladding layer and coating, 1.5-µm AlGaInAs/InP multiple quantum well (MQW) CPM lasers with high-power and ultra-short pulse generation capability at a repetition rate of 100 GHz are reported. The laser adopts a high-power epitaxial design, with four pairs of MQWs and an asymmetrical dilute waveguide cladding layer to reduce the internal loss, maintaining good thermal conductivity while increasing the saturation energy of the gain region. The asymmetric coating is introduced, as compared to conventional CPM laser with symmetric reflectivity, to further increase the output power and shorten the pulse width. With a high reflection (HR) coating of 95% on one facet and another facet as cleaved, 100-GHz sub-picosecond optical pulses with peak power on a Watt level are demonstrated. Two mode-locking states, the pure CPM state and the partial CPM state, are investigated. Pedestal-free optical pulses are obtained for both states. For the pure CPM state, a pulse width of 564 fs, an average power of 59 mW, a peak power of 1.02 W, and an intermediate mode suppression ratio over 40 dB are demonstrated. For the partial CPM state, a pulse width of 298 fs is demonstrated.

1.3 µm InGaAlAs/InP laser integrated with laterally tapered SSC in a reverse mesa shape.

We report 1.3 µm InGaAlAs/InP lasers integrated with laterally tapered spot size converter (SSC) in reverse mesa shape. Because the top width is significantly larger than the bottom width for the reverse mesa ridge, high quality SSCs having narrow tip width can be fabricated through conventional photolithography with a high reproductivity. The Threshold current of the fabricated 1000 µm long SSC integrated device is 25 mA and 44 mW single facet optical power can be obtained at 300 mA current. The lateral and vertical divergence angles are as low as 8 ° and 11°, respectively.

Up to 50 Gb/s modulation of an EAM integrated widely tunable DBR laser.

An electro-absorption modulator (EAM) integrated widely tunable distributed Bragg reflector (DBR) laser working at 1.5 µm is reported. By utilizing the RF resonance between the bonding wire and the EAM, a 28 GHz modulation bandwidth is obtained. The device is modulated with up to 50 Gb/s NRZ data. At 28 Gb/s, the power penalty to obtain a 10-10 bit error rate (BER) after a 5 Km standard single mode fiber transmission is less than 0.7 dB. Because the DBR material has a long bandgap wavelength, the wavelength tuning range of the laser is larger than 12 nm. The DBR laser is a promising low cost tunable light source for future high capacity wavelength division multiplexing (WDM) optical communication systems.

Dual-wavelength DBR laser integrated with high-speed EAM for THz communications.

We report a novel single-cavity dual-wavelength laser that has two distributed Bragg reflector (DBR) gratings at each side of a gain section for THz communication applications. By varying the inject current of one of the DBR gratings, the optical beat frequency of the laser can be widely tuned. In the device, a high-speed electro-absorption modulator (EAM) is also integrated and can be used for up to 25 Gb/s data modulation.

Reflection Airy distribution of a Fabry-Pérot resonator and its application in waveguide loss measurement.

The reflection Airy distribution (RAD) of a Fabry-Pérot (F-P) resonator is deduced with the consideration of the mode coupling between the cavity resonance field and the initial back-reflected field at the input F-P resonator facet, as well as the influence of the loss/gain factor. A waveguide loss/gain measurement method is proposed based on the measurement of the finesse of the RAD, which is intrinsically free from the influence of the coupling loss and the substrate scattering noise. The waveguide loss can be measured with a simple single-facet coupling setup, considerably reducing the coupling difficulty and the complexity of the measurement system while achieving the same or better measurement accuracy as that of the transmission F-P method.

Comprehensive comparison of multiple quantitative near-infrared spectroscopy models for Aspergillus flavus contamination detection in peanut.

BACKGROUND: Aspergillus flavus is a major pollutant in moldy peanuts, and it has a large influence on the taste of food. The secondary metabolites of Aspergillus flavus, including aflatoxin B1 (AFB1) and aflatoxin B2 (AFB2), are highly toxic and can expose humans to high risk. The total mold count (TMC) is an important index to determine the contamination degree and hygiene quality of peanut. RESULTS: Quantitative calibration models were established based on full-band wavelengths and characteristic wavelengths, combined with chemometric methods, to explore the feasibility of the use of near-infrared spectroscopy (NIRS) for rapid detection of the TMC in peanuts. The successive projection algorithm (SPA) and elimination of uninformative variables (UVE) algorithms were used to extract the characteristic wavelengths. In comparison, the model built by original spectrum, selected with the UVE algorithm, gave the best result, with a correlation coefficient in a prediction set (RP ) of 0.9577, a root mean square error for the prediction set (RMSEP) of 0.2336 Log CFU/g, and a residual predictive deviation (RPD) of 3.5041. CONCLUSIONS: The results showed that NIRS is a rapid, practicable method for the quantitative detection of peanut Aspergillus flavus contamination. It is a promising method for detecting moldy peanuts and increasing peanut safety. © 2019 Society of Chemical Industry.

High-speed directly modulated widely tunable two-section InGaAlAs DBR lasers.

We report widely tunable two-section distributed Bragg reflector (DBR) lasers, which have InGaAlAs multiple quantum wells (MQWs) as the gain material. By butt-jointing InGaAsP, which has a photoluminescence wavelength of 1.4 µm as the material of the DBR section, a wavelength tuning range of 12 nm can be obtained by current injection into the DBR section. The direct modulation bandwidth of the lasers is greater than 10 GHz over the entire wavelength tuning range up to 40°C. Compared with InGaAsP DBR lasers having the same structure, the InGaAlAs lasers have smaller variations in both the threshold current and slope efficiency with the temperature because of the better electron confinement in the InGaAlAs MQWs. Moreover, the DBR-current-induced decreases in the modulation bandwidth and side mode suppression ratio (SMSR) of the optical spectra are notably smaller for the InGaAlAs lasers than for the InGaAsP lasers.

Long-range and high-resolution correlation optical time-domain reflectometry using a monolithic integrated broadband chaotic laser.

We experimentally demonstrate a compact, long-range, high-resolution chaotic correlation optical time-domain reflectometry based on a monolithic integrated chaotic laser (MICL). The MICL can directly generate a broadband chaotic signal covering a RF frequency range of over 40 GHz. Multi-reflection events can be precisely located in a detection range of ∼47 km with a range-independent resolution of 2.6 mm.

Three-coherent-output narrow-linewidth and tunable single frequency 1x2 multi-mode-interferometer laser diode.

A 1x2 multi-mode-interferometer (MMI) laser diode was successfully designed and fabricated, which demonstrated three coherent outputs of tunable single frequency emission with more than 30dB side mode suppression ratio (SMSR), a tuning range of 25nm in C and L band, as well as 750 kHz linewidth. This 1x2 MMI laser could be expanded to more advanced configurations such as 1xN or MxN (M≥1, N>2) MMI lasers to achieve a multiple coherent output source. In addition, these lasers do not require material regrowth and high resolution gratings which can significantly increase the yield and reduce the cost.

Widely tunable monolithic dual-mode laser for W-band photonic millimeter-wave generation and all-optical clock recovery.

We demonstrate a monolithic dual-mode amplified feedback laser for photonic millimeter-wave generation and all-optical clock recovery. Dual-mode lasing with beating frequency around 100 GHz was realized by using a single-mode distributed feedback (DFB) laser with a short feedback cavity that was integrated by simple quantum-well intermixing technology. By tuning the bias currents of the laser sections, the beating-frequency can be continuously tuned from 75 to 109 GHz, almost covering the entire W-band (75-110 GHz). Furthermore, by using this device, an all-optical clock recovery for 100 Gbit/s return-to-zero on-off-keying signal was achieved with a timing jitter of 301 fs.

Frequency-tunable optoelectronic oscillator using a dual-mode amplified feedback laser as an electrically controlled active microwave photonic filter.

A widely tunable optoelectronic oscillator (OEO) based on a self-injection-locked monolithic dual-mode amplified feedback laser (DM-AFL) is proposed and experimentally demonstrated. In the proposed OEO structure, the DM-AFL functions as an active tunable microwave photonic filter (MPF). By tuning the injection current applied on the amplifier section of the AFL, tunable microwave outputs ranging from 32 to 41 GHz and single sideband phase noises below -97 dBc/Hz at 10 kHz offset from the carriers were realized.

Ground-state lasing in high-power InAs/GaAs quantum dots-in-a-well laser using active multimode interference structure.

We have designed and demonstrated InAs/GaAs quantum dots-in-a-well laser diodes for short cavities with transverse fundamental mode operation by using an active multimode interferometer (MMI) structure for the first time to the best of our knowledge. Room-temperature continuous-wave ground-state lasing at 1280 nm has been achieved with an output power of 116 mW per facet, which is 2.4 times higher than that of the conventional ridge laser diodes. By using the MMI structures, the excited-state (ES) lasing is effectively suppressed with no ES lasing, even at a high injection current of 400 mA. This device has great potential for high-power single-mode laser emission with low electric power consumption and simple fabrication processes.

Electroabsorption-modulated widely tunable DBR laser transmitter for WDM-PONs.

We present an InP based distributed Bragg reflector (DBR) laser transmitter which has a wide wavelength tuning range and a high chip output power for wavelength division multiplexing passive optical network (WDM-PON) applications. By butt-jointing InGaAsP with 1.45 µm emission wavelength as the material of the grating section, the laser wavelength can be tuned for over 13 nm by the DBR current. Accompanied by varying the chip temperature, the tuning range can be further enlarged to 16 nm. With the help of the integrated semiconductor optical amplifier (SOA), the largest chip output power is over 30 mW. The electroabsorption modulator (EAM) is integrated into the device by the selective-area growth (SAG) technique. The 3 dB small signal modulation bandwidth of the EAM is over 13 GHz. The device has both a simple tuning scheme and a simple fabrication procedure, making it suitable for low cost massive production which is desirable for WDM-PON uses.

Tunable optical microwave generation using self-injection locked monolithic dual-wavelength amplified feedback laser.

A tunable optical microwave generation scheme using self-injection locked monolithic dual-wavelength amplified feedback laser (AFL) is proposed and experimentally demonstrated. By using a dual-loop feedback scheme, the 3-dB linewidth of the optical microwave output resulting from mode beating is reduced from MHz to kHz scale. Optical microwave generation tunable from 30 to 38 GHz with 3-dB linewidth below 2 kHz is experimentally demonstrated.

Direct generation of broadband chaos by a monolithic integrated semiconductor laser chip.

A solitary monolithic integrated semiconductor laser (MISL) chip with a size of 780 micrometer is designed and fabricated for broadband chaos generation. Such a MISL chip consists of a DFB section, a phase section and an amplification section. Test results indicate that under suitable operation conditions, this laser chip can be driven into broadband chaos. The generated chaos covers an RF frequency range, limited by our measurement device, of 26.5GHz, and possesses significant dimension and complexity. Moreover, the routes into and out of chaos are also characterized through extracting variety dynamical states of temporal waveforms, phase portraits, RF spectra and statistical indicators.

Detailed analysis of a 40 GHz all-optical synchronization based on an amplified-feedback distributed feedback laser.

We demonstrate an all-optical synchronization using an amplified-feedback distributed feedback laser with coherent injection experimentally, which can synchronize 40 GHz degraded signals even with optical signal-to-noise ratio as low as 5 dB, or chromatic dispersion as large as 408 ps/nm. Besides, this optical synchronization has a large range of power operation, i.e. high sensitivity of synchronization, from -21.40 dBm to -8.23 dBm, as well as a large frequency-locking range of 190 MHz.

40 Gbits/s all-optical clock recovery for degraded signals using an amplified feedback laser.

All-optical clock recovery for the return-to-zero modulation format is demonstrated experimentally at 40 Gbits/s by using an amplified feedback laser. A 40 GHz optical clock with a root-mean-square (rms) timing jitter of 130 fs and a carrier-to-noise ratio of 42 dB is obtained. Also, a 40 GHz optical clock with timing jitter of 137 fs is directly recovered from pseudo-non-return-to-zero signals degraded by polarization-mode dispersion (PMD). No preprocessing stage to enhance the clock tone is used. The rms timing jitter of the recovered clock is investigated for different values of input power and for varying amounts of waveform distortion due to PMD.

640-Gbit/s fast physical random number generation using a broadband chaotic semiconductor laser.

An ultra-fast physical random number generator is demonstrated utilizing a photonic integrated device based broadband chaotic source with a simple post data processing method. The compact chaotic source is implemented by using a monolithic integrated dual-mode amplified feedback laser (AFL) with self-injection, where a robust chaotic signal with RF frequency coverage of above 50 GHz and flatness of ±3.6 dB is generated. By using 4-least significant bits (LSBs) retaining from the 8-bit digitization of the chaotic waveform, random sequences with a bit-rate up to 640 Gbit/s (160 GS/s × 4 bits) are realized. The generated random bits have passed each of the fifteen NIST statistics tests (NIST SP800-22), indicating its randomness for practical applications.