The search for low-cost, scalable alternatives to high vacuum-based thin film synthesis has been reinvigorated by recent developments in fields like solution processing, additive manufacturing, and laser processing. In this work we demonstrate the viability and development of a novel method which combines solution-based synthesis of mesoporous niobium oxide thin films and laser spike annealing in a reactive ammonia environment to form niobium nitride (NbN) films. A custom-designed small-scale thin film environmental cell reactor was engineered to conduct localized, rapid thermal processing of thin films using a 980 nm diode laser in reactive ambients. Through iterative design modifications and testing, an optimized reactor capable of handling toxic gases like ammonia, and dissipating heat generated by the laser on milli-second time scales was developed.Systematic experiments were carried out using the lateral gradient laser spike annealing (lg-LSA) technique, which enables spatial control over the processing temperature and reaction times. Characterization by SEM, EDS, synchrotron XRD, and reflectance spectroscopy showed the successful conversion of niobium oxide to niobium nitride in the regions exposed to peak processing temperatures above 1250-1350°C. The spatial gradient enabled the mapping of the phase evolution. Synchrotron XRD confirmed the formation of the cubic-NbN phase, and SEM images show retention of the mesoporous structure for temperatures below 1200°C. The structure and composition of the films laser-annealed resembled those annealed in a furnace, despite processing times that were reduced to milliseconds from 10-12 hours. This work demonstrated the feasibility of integrating solution processing with laser spike annealing to create functional quantum materials.