Semiconductor broadband light emitters have emerged as ideal and vital light sources for a range of biomedical sensing/imaging applications,especially for optical coherence tomography systems.Although near-infrared broadband light emitters have found increasingly wide utilization in these imaging applications,the requirement to simultaneously achieve both a high spectral bandwidth and output power is still challenging for such devices.Owing to the relatively weak amplified spontaneous emission,as a consequence of the very short non-radiative carrier lifetime of the inter-subband transitions in quantum cascade structures,it is even more challenging to obtain desirable mid-infrared broadband light emitters.There have been great efforts in the past 20 years to pursue high-efficiency broadband optical gain and very low reflectivity in waveguide structures,which are two key factors determining the performance of broadband light emitters.Here we describe the realization of a high continuous wave light power of ＞ 20 mW and broadband width of ＞ 130 nm with near-infrared broadband light emitters and the first mid-infrared broadband light emitters operating under continuous wave mode at room temperature by employing a modulation p-doped InGaAs/GaAs quantum dot active region with a ‘J’-shape ridge waveguide structure and a quantum cascade active region with a dual-end analogous monolithic integrated tapered waveguide structure,respectively.This work is of great importance to improve the performance of existing near-infrared optical coherence tomography systems and describes a major advance toward reliable and costeffective mid-infrared imaging and sensing systems,which do not presently exist due to the lack of appropriate low-coherence mid-infrared semiconductor broadband light sources.