Qiaoyin Lu

Analysis of Slot Characteristics in Slotted Single-Mode Semiconductor Lasers Using the 2-D Scattering Matrix Method

We use the two-dimensional (2-D) scattering matrix method (SMM) to analyze the slot characteristics in slotted single-mode semiconductor lasers and compare the results with those calculated by the one-dimensional transfer matrix method (TMM). The analysis shows that the 2-D SMM is required to accurately account for the measured results. Using the 2-D SMM simulation, we find that there is almost no reflection at the interface from slot to waveguide while a large reflection exists at the interface from waveguide to slot, and the power loss is much larger than the power reflected. For a single slot, the slot width has little influence on the slot reflectivity, which coincides with the measured results. The reflection and transmission of the slot are found to be exponentially dependent on the slot depth

A Novel Two-Section Tunable Discrete Mode Fabry-PÉrot Laser Exhibiting Nanosecond Wavelength Switching

A novel widely tunable laser diode is proposed and demonstrated. Mode selection occurs by etching perturbing slots into the laser ridge. A two-section device is realized with different slot patterns in each section allowing Vernier tuning. The laser operates at 1.3 mum and achieves a maximum output power of 10 mW. A discontinuous tuning range of 30 nm was achieved with a side mode suppression greater than 30 dB. Wavelength switching times of approximately 1.5 ns between a number of wavelength channels separated by 7 nm have been demonstrated.

Design of Slotted Single-Mode Lasers Suitable for Photonic Integration

A single-mode laser structure suitable for photonic integration is presented. The laser can be fabricated by standard photolithography without any regrowth steps. Through optimization, a threshold current as low as 13 mA and a sidemode suppression ratio (SMSR) up to 47 dB have been predicted for a 400-¿m-long laser. A high yield up to 90% is also predicted with the requirement that the SMSR is higher than 40 dB at an injection current of 100 mA.

Integrable Slotted Single-Mode Lasers

A single-mode laser structure based on slots suitable for monolithic photonic integration is presented. The laser can be fabricated by photolithography without any regrowth steps. Stable single-mode performance with a sidemode suppression ratio up to 50 dB at twice threshold has been demonstrated for the fabricated lasers.

Single mode lasers based on slots suitable for photonic integration

The single mode laser structure based on etched slots suitable for photonic integration is presented in this paper. The laser is made completely dependent on a group of slots on one side of the laser cavity. The fabricated 750 μm long single section laser exhibits a threshold current and a slope efficiency of about 32 mA and 0.11 mW/mA, respectively. The stable single mode operation has been observed with a side mode suppression ratio (SMSR) of around 47 dB at a current injection of 100 mA for the fabricated laser. To solve the yield problem associated with the cleaving of the laser structure, the two-section single mode laser based on slots was further present. By tuning the back section current, stable single mode performance with a SMSR of more than 42 dB is observed over a wide temperature from 15°C to 65°C for the fabricated 750 μm long two-section laser. The presented laser structure just needs a single wafer growth and can be fabricated by standard photolithography and has very strong potential for use in optical communication systems.

Enhancement of quality factor for TE whispering-gallery modes in microcylinder resonators

The enhancement of quality factor for TE whispering-gallery modes is analyzed for three-dimensional microcylinder resonators based on the destructive interference between vertical leakage modes. In the microcylinder resonator, the TE whispering-gallery modes can couple with vertical propagation modes, which results in vertical radiation loss and low quality factors. However, the vertical loss can be canceled by choosing appropriate thickness of the upper cladding layer or radius of the microcylinder. A mode quality factor increase by three orders of magnitude is predicted by finite-difference time-domain simulation. Furthermore, the condition of vertical leakage cancellation is analyzed.

Fabry–Pérot Laser Characterization Based on the Amplified Spontaneous Emission Spectrum and the Fourier Series Expansion Method

Comprehensive Fabry-Pérot laser characterization based on measurements of the amplified spontaneous emission spectrum analyzed using the Fourier series expansion method is presented. The parameters of net modal gain, internal loss, quasi-Fermi level separation, linewidth enhancement factor, injection efficiency, and geometric spontaneous emission factor can all be extracted.

Determination of Internal Loss and Quasi-Fermi Level Separation From the Amplified Spontaneous Emission Spectrum of Fabry–PÉrot Semiconductor Lasers

The net modal gain and the un-amplified spontaneous emission (ASE) coupled into the laser waveguide mode are extracted from the ASE spectrum of Fabry-Perot semiconductor lasers by the Fourier transform method with a deconvolution process. Highly accurate quasi-Fermi level separation and internal loss are then derived by a minimum search process from the relationship between the spontaneous emission and gain

Design of Low

GaAs-based electrooptic phase modulators using an n-i-p-n structure and coplanar waveguide traveling-wave electrodes are designed using the compact 2-D finite-difference time-domain technique and Pade approximation transform. By optimization, an electrical 3-dB bandwidth of 40 GHz and a 6.6-V V pi are predicted for a 5-mm-long modulator.

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We present an improved design of a wavelength-tunable single-mode laser array based on a high order surface grating with non-uniformly spaced slots. The laser array consists of 12 slotted single-mode lasers. The fabricated device exhibits a quasi-continuous tuning range of more than 36 nm over the temperature range from 10°C - 45°C covering the full C-band. All lasers in the array have stable single-mode operation with side mode suppression ratio of 50 dB due to the modified slot design. A spectral linewidth of less than 500 kHz was obtained for all channels in the array.