An Nd:YAG laser is generally used as the optical source for photoacoustic imaging (PAI) systems, which support a high-power pulsed laser. However, PAI systems based on Nd:YAG lasers have several disadvantages, such as instability against impact and vibration, poor mobility, and large size. To overcome the limitations, we demonstrate a PAI system using a master oscillator power amplifier (MOPA) fiber laser and an arrayed ultrasound transducer. The fabricated MOPA fiber laser has a variable repetition rate in the range of 1–50 kHz, a pulse width of 10–70 ns, and an output power of 160 μJ. Furthermore, it is stable to impact and vibration, mobile, and compact with a size of 427×250×170 mm<sup>3</sup>. We achieved PAI 150 times faster using MOPA fiber laser than using Nd:YAG laser with the arrayed ultrasound transducer composed of 128 elements. Therefore, we believe that the PAI system based on the MOPA fiber laser has significant potential for use as a clinical ultrasound imaging system.
A 16-arrayed polymeric optical modulator is fabricated using an electro-optic (EO) polymer with a large EO coefficient and good thermal stability. The 16-arrayed modulator has lumped type electrodes with a response time of less than one nanosecond. The 16-arrayed modulator has good uniform modulation characteristics between the individual modulators. The deviation of half-wave voltages is 0.2 V and that of insertion losses about 1 dB. Crosstalks range from -28 to -36dB and extinction ratios are more than 21 dB.
Recently, we developed a wavelength converter, a 16-arrayed electro-optic (EO) Mach-Zehnder (MZ) modulator, polarization adjustable and athermal arrayed waveguide gratings (AWGs), and a wavelength channel selector by using all polymers. We designed and fabricated periodically poled nonlinear optical (NLO) polymer waveguides for the wavelength converter. Difference-frequency generation (DFG) process with a quasi-phase-matching (QPM) scheme was used. An all polymer-based wavelength channel selector composed of 16-channel EO polymer modulator array between two polymer AWGs is proposed and fabricated using chip-to-chip bonding of the three optical polymeric waveguide devices. For this, the 16-arrayed polymeric optical modulator and AWGs are respectively fabricated using EO and low-loss optical polymers. For these two-typed devices, we have synthesized new side chain NLO polymers and used low-loss optical polymers, designed and developed by ZenPhotonics, Inc. The developed these photonic devices were discussed in details from materials to packaging.