Current linear modulators offer limited bandwidth and spurious-free dynamic range (SFDR) as electro-optic modulators and power handling as directly modulated lasers—also incurring high insertion loss and high Vpi. Recently developed at UCF, a new linear modulator with potentially infinite SFDR and multi-gigahertz bandwidth offers possible negative insertion loss and very low Vpi, in the range of few milivolts, compared to existing technologies. While a conventional method for linearizing modulators uses a complicated feedforward electrical circuit to correct for nonlinearities, with still-limited SFDR, the new technology offers pure linear response without the need for a correcting circuit. This linear optical modulator is useful in signal processing, fiber optic communication, frequency comb sources, computer interconnect, radio frequency communication, and radio frequency synthesis.
The new linear optical modulator achieves a linear response by phase modulating the output of an injection locked slave laser, or modulating the resonance of an injection locked slave laser, and combining the modulated output with the injection source signal from the master laser. The modulator uses a resonant cavity in one arm of a Mach Zehnder interferometer. The output frequency of the resonant cavity device, the same as the injected signal, collects a phase related to the frequency difference—the resonant cavity frequency and the detuning of the injected cavity frequency, leading to the arcsine of the detuning. Combining the arcsine phase modulated signal with a coherent signal creates a detected signal following the standard interferometer expression.
- Potentially infinite SFDR
- Multi-GHz bandwidth
- Negative insertion loss
- Very low Vpi
- No need for a correcting circuit
- Signal processing
- Fiber optic communication
- Frequency comb sources
- Computer interconnect
- Radio frequency communication and synthesis