Optical Generation of Rapidly Tunable Millimeter Wave Subcarrier

This paper concerns an optically generated MgO:LiNb03 crystal, rapidly tunable millimeter wave source. The millimeter is the tuning section. The two side-.,ywave signal is generated by beating the output of two side lasers are pumped by an 808nm high Nd:YV04 / MgO:LiNb03 single mode microchip laser sections realized monolithically in a single composite power laser diode source. Electrodes are crystal. The device can be tuned from DC to 100 GHz. deposited on the toD and the bottom of the 1.2 medium, and a 1.2 The measured tuning sensitivity is 8.8MHzNolt, and the tuning rate is over 10 THz/sec. & MgO:LiNb03 iuning section. The outputs of the two single mode lasers are combined, Introduction Numerous applications like frequency chirped lidar-radar, ra&o over fiber and biomedical imaging, require optical transmitters that can generate rapidly tunable millimeter wave sub-carriers. Specifically, for accurate range measurements in underwater detection or biomedical probing of tissues [I], a rapidly tunable optical source is required. Semiconductor laser diodes can be tuned rapidly, but their performance is limited due to their inherently high noise. Compact, efficient solid-state microchip lasers, with high spectral quality, show great potential as optical transmitters for these applications. Optical heterodyning of two ring-oscillators for millimeter-wave generation has been reported [2]. However, these approaches employ thermal or PZT tuning, which are essentially very slow processes. To overcome this problem, a monolithic microchip laser system, with electro-optical tenability, was fabricated. coupled into a single mode fiber and transmitted to a high-speed optical detector. By applying an electrical field to one of the lasers, its refractive index is modulated, which shifts its lasing wavelength resulting in a variable millimeter wave signal. In this heterodyned arrangement, the difference in the optical wavelengths, AAopt, gives rise to the millimeter wave beat frequency, fm=c AAopt/Aop?. The monolithic configuration gives the device simplicity, compactness, stability, and reduced sensitivity to external temperature fluctuations. The actual device, mounted on a brass fixture, is depicted in Fig.2.