SBIR-STTR Award

In the proposed work we will investigate the THz properties of a slab waveguide made from a GaP or ZnGeP2 wafer. We plan to investigate how the width of a slab waveguide will affect the output power of the THz waves and normalized conversion efficiencies. We are particularly interested in the exploration of how the multi-modes supported by the waveguide will affect the THz parametric conversion due to the interference among the multi-modes. We expect that the normalized conversion efficiencies will be significantly increased by using a slab waveguide. Following our results, we are going to design, fabricate, and characterize a novel coupled-waveguide structure in which a slab GaP or ZnGeP2 waveguide is coupled to an adjacent waveguide made from a polymer material by a thin polymer layer. The idea behind this is to couple the THz wave from an electro-optic crystal to a polymer waveguide before it is absorbed by the electro-optic crystal. According to our previous theory, this is equivalent to the increase of the interaction length among the three parametric waves within the electro-optic crystal, and therefore, the output power and conversion efficiencies for the THz generation can be increased by one order of magnitude. The coupling layer can be fabricated in such a way that it serves as a confinement layer for the two waveguides and it is used to achieve the phase-matching for the parametric conversion. We will use the method of diffusion-bonding technique to bond the electro-optic crystal and polymer wafers together. We will experimentally determine the condition for fabricating such a high-quality waveguide structure by using this technique. Since in such a case the polymer plate does not have to be poled, we could just use any low-loss polymer such as polyethylene. We will use our ultrafast laser pulses to characterize such a novel structure by measuring the THz output characteristics such as the central wavelength, linewidith, conversion efficiencies, and coupling efficiencies. Following our result, we will optimize our coupled-waveguide structure in order to further improve the normalized conversion efficiencies. We also plan to carry out comprehensive study and design for a prototype device which can produce an output power of more than 10 W. In addition, we are going to identify key sub-components for the device with a tuning range of 0.3-10 THz. Furthermore, we will complete a feasibility study on the increase of a conversion efficiency to about 1%.

In this Phase II proposal from the ArkLight/Lehigh team, we propose to investigate variety of semiconductor and polymeric electro-optic crystals and materials with one of our goals for scaling up the output powers of the THz sources. We are going to explore a class of the novel THz components combined with many novel configurations with one of our objectives for further increasing the output powers of the THz sources, from simple slab waveguides to photonic crystals. We will also study the possibility of implementing the single-element chemical sensor and multiple-element chemical sensor array. Specifically, we will reduce the linewidth reduction of 532-nm pump laser down to 0.000024 wave number. We plan to implement a narrow-linewidth optical-parametric oscillator for producing the signal and idler waves necessary for efficient THz generation. We will achieve the state-of-art performance for a coherent THz source based on frequency mixing in an optimized GaP crystal. We plan to design and to implement a THz frequency upconverter based on a GaP crystal. We are going to integrate a THz source with a detection system and then to perform system testing. We will design, fabricate, and test variety of different waveguides for enhancing the normalized conversion efficiencies from optical pulses to the THz output. We plan to design, to fabricate, and to test a THz generator and frequency upconverter based on waveguides. We are going to deign, fabricate, and test Bragg reflectors, filters, and beamsplitters working in the THz region. We will investigate the potential of THz photonic crystal devices. We will design, fabricate, and test attenuated reflection device. We will optimize the waveguide for further enhancing the conversion efficiencies. We will implement high-Q cavity for multiple passes. We will design, fabricate, and test different configurations for compact sources and frequency upconverters. We will design and simulate single-element chemical sensor. We will also deign and simulate multiple-element chemical sensor array.

Keywords:
Thz Materials, Electro-Optic Crystals, Electro-Optic Polymers, Thz Optoelectronic Devices, Thz Chemical Sensors, High-Power Thz Sources, Thz Waveguide