GHz 3dB Bandwidth Research Articles

Design and Simulation of a 0.23-THz Extended Interaction Amplifier With Trapezoid-Neck Cavities

We address extended interaction amplifier (EIA) and put forward a novel resonant cavity design based on a traditional ladder-type resonant cavity combined with symmetrically trapezoidal neck cavities. The resonant cavity exploits a three-gap structure with characteristic impedance higher than the corresponding single-gap structure. The effects of the trapezoidal necks are analyzed for the TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">31</sub> - 2π mode in the terahertz range. To broaden the gain bandwidth of the EIA, a stagger-tuning method is employed, and a six-cavity structure is proposed. After the stagger-tuning state, the designed multicavity EIA produces stable output power from a 20-mW input driving signal, with a gain of about 35.05 dB and efficiency 1.51% at 0.23 THz, with more than 1.1 GHz-3 dB bandwidth when a sheet beam with a dimension of 0.7 mm × 0.1 mm, 14.7-kV voltage and 0.29-A current passes through the beam tunnel.

1.3 μm p-Modulation Doped InGaAs/GaAs Quantum Dot Lasers with High Speed Direct Modulation Rate and Strong Optical Feedback Resistance

Aiming to realize high-speed optical transmitters for isolator-free telecommunication systems, 1.3 μm p-modulation doped InGaAs/GaAs quantum dot (QD) lasers with a 400 μm long cavity have been reported. Compared with the un-doped QD laser as a reference, the p-doped QD laser emits at ground state, with an ultra-low threshold current and a high maximum output power. The p-doped QD laser also shows enhanced dynamic characteristics, with a 10 Gb/s large-signal direct modulation rate and a 7.8 GHz 3dB-bandwidth. In addition, the p-doped QD laser exhibits a strong coherent optical feedback resistance, which might be beyond −9 dB.

Polarization-independent atomic prism filter for removing amplified spontaneous emission.

We create an optical frequency, polarization-independent, narrow bandpass filter of 1.3GHz (3dB bandwidth), using the steep dispersion near the rubidium D1 atomic transitions within a prism-shaped vapor cell. This enables us to clean the amplified spontaneous emission from a laser by more than 3 orders of magnitude. Such a filter could find uses in fields such as quantum information processing and Raman spectroscopy.

Laser direct writing of 40 GHz RF components on flexible substrates

Flexible electronics have emerged as a very promising alternative of CMOS compatible electronics for a plethora of applications. Laser microfabrication techniques, such as selective laser patterning and sintering are compatible with flexible substrates and have demonstrated impressive results in the field of flexible electronic circuits and sensors. However, laser based manufacturing of radio frequency (RF) passive components or devices is still at an early stage. In this work we report on the all-laser fabrication of Silver Co-Planar Waveguides (CPWs) on polyethylene-naphthalate (PEN) substrates employing flat-top optics to achieve uniform laser fluence and thus high fabrication precision and reproducibility but also to mitigate the thermal effects of nanosecond laser pulses. The CPWs have been fabricated to match the impedance of 50Ω ports of an Anritsu vector network analyzer operating from 40MHz to 40GHz. The all laser fabrication process consisted in the selective laser sintering of square dies on a Silver Nano Particle layer spin-coated on a PEN substrate followed by the selective laser patterning of the CPWs with a ns pulsed Nd:YAG laser source operating at 532nm, according to the optimized parameters extracted from a previous studies of the authors. The CPWs have been characterized electrically at the 0.04–40GHz regime and found to be excellent transmission lines with a 40GHz 3dB bandwidth, owing to the high electrical conductivity of Ag and the excellent dielectric properties of PEN. This novel process is a milestone towards the RF technology transfer to flexible electronics with low cost and specs comparable to the CMOS compatible equivalents.

Operation of low driving voltage cascaded modulator over non-cascaded modulator for 4 dB extinction ratio at 100 giga bit per second (Gbps)

This paper describes improved results when comparing cascaded traveling wave electro absorption modulator (TWEAM) to non-cascaded TWEAM by simulation. Large signal modeling is used for both types of modulators to achieve 4 and 10dB extinction ratios (ERs) with flat frequency response for applications in short distance as well as long distance optical fiber communication. To obtain 4 and 10dB ERs with 110GHz 3dB bandwidth, a cascaded TWEAM requires 0.4V peak to peak (VP-P) and 1 VP-P input driving voltages respectively. A non-cascaded TWEAM requires about two times the input driving voltage compared to the cascaded modulator to achieve the same values of ER and 3dB bandwidth. Both modulators have been simulated with the same bias and also use the same circuit parameters except for the total active segment lengths (1 and 0.5mm for cascaded and non-cascaded modulator respectively) and microstrip lengths to obtain the same ERs and 3dB bandwidths.

Amplitude modulation filtering of FM-to-AM conversion due to the focusing grating of LMJ

FM-to-AM conversion is an important issue for high power lasers such as the Laser MegaJoule. Indeed temporal intensity modulation may prevent a good ignition of the target. FM is necessary to achieve optical smoothing: phase modulation broadens the spectrum and the different generated wavelengths will create different speckle patterns thanks to dispersion systems (gratings) that spatially average the focal spot on the target. We show in this paper that dispersion and focusing systems linearly filter intensity modulations by averaging due to time delay introduced by the gratings. For the LMJ configuration this filter is equivalent to a Gaussian low-pass filter with a 7GHz 3dB-bandwidth.

10 GHz optical short pulse generation using tandem electroabsorption modulators monolithically integrated with distributed feedback laser by ultra-low-pressure selective area growth

In this work, a novel light source of tandem InGaAsP/InGaAsP multiple quantum well electroabsoption modulator(EAM) monolithically integrated with distributed feedback laser is fabricated by ultra-low-pressure (22×１０２Pa) selective area growth metal-organic chemical vapor diposition technique. Superior device performances have been obtained, such as low threshold current of 19 mA, output light power of 4.5 mW, and over 20 dB extinction ratio at 5 V applied voltage when coupled into a single mode fiber. Over 10 GHz 3dB bandwidth in EAM part is developed with a driving voltage of 2 V. Using this sinusoidal voltage driven integrated device, 10GHz repetition rate pulse with an actual width of 13.7 ps without any compression elements is obtained due to the gate operation effect of tandem EAMs.