Non-ambiguous Range Extension by a Frequency Scanning Soliton Microcomb

Laser based range measurement system plays an important role in both scientific and industrial areas. Soliton microcomb (SMC) based dispersive interferometry (DPI) method has shown the advantages of high speed, high precision, and compact size in ranging systems. However, due to the high repetition rate of SMCs, it results in a small non-ambiguous range (NAR), which impacts the practical application of SMC based ranging systems. Furthermore, when the measured distance is close to N times NAR, it is difficult to extract the distance information including the delay time and direction. Here, we introduce frequency scanning and prime number algorithm to an SMC based DPI ranging system. The frequency of SMC can be scanned over one free spectral range (FSR) by sweeping the pump frequency and the resonance of the microresonator synchronously. The interference spectra are recorded when the frequency is scanned every $1/{{{\bm{i}}}_{\bm{m}}}({\bm{\ }}{{{\bm{i}}}_{\bm{m}}} = $ 2, 3, 5, 7…, a list of primes) FSR, and the NAR can be extended by $\sim \sqrt {2\prod {{{\bm{i}}}_{\bm{m}}}} $ times through interpolating the recorded interference spectra. We experimentally verify the feasibility of the proposed ranging system, and the NAR is extended by 3 times. Furthermore, we extract a small delay time of 6.859 fs with a standard deviation of 1.128 μm, which cannot be determined by the SMC with original repetition rate. The proposed ranging system can extend the NAR without any auxiliary rough measurement systems, and the detectable distance over the full range can be achieved.