SE INVESTIGA TEÓRICAMENTE EL EFECTO DE LA DISPERSIÓN ESPACIAL EN UNA PELÍCULA SEMICONDUCTORA CON RUGOSIDAD SUPERFICIAL ALEATORIA, DEPOSITADA SOBRE UN SUBSTRATO METÁLICO, SOBRE EL COEFICIENTE DE REFLEXIÓN DIFERENCIAL. LA INVESTIGACIÓN SE REALIZA CERCA DE LA RESONANCIA EXCITÓNICA DONDE LA NO-LOCALIDAD ES FUERTE Y CONDUCE A LA GENERACIÓN DE ONDAS POLARITÓNICAS ADICIONALES. APLICANDO UNA TEORÍA DE PERTURBACIÓN A PRIMER ORDEN, CALCULAMOS LAS DEPENDENCIAS ANGULAR Y DE FRECUENCIA DEL COEFICIENTE DE REFLEXIÓN DIFERENCIAL PARA EL CASO DE UNA RUGOSIDAD UNIDIMENSIONAL. LOS ESPECTROS DE REFLEXIÓN DIFUSA DE CUCL SOBRE UN METAL DE AL PARA LUZ INCIDENTE CON POLARIZACIÓN S PRESENTAN RESONANCIAS PRONUNCIADAS (PICOS) EN LAS FRECUENCIAS QUE SATISFACEN LAS CONDICIONES FABRY-PEROT PARA LOS MODOS POLARITÓNICOS ADICIONALES. ESTAS CONDICIONES CORRESPONDEN TAMBIÉN A LA CUANTIZACIÓN DEL MOVIMIENTO TRANSLACIONAL DEL EXCITÓN. NUESTROS RESULTADOS MUESTRAN LA UTILIDAD DEL ESPECTRO DE REFLEXIÓN DIFUSA PARA ESTUDIAR LA EXCITACIÓN DE LOS MODOS POLARITÓNICOS CUANTIZADOS EN PELÍCULAS NO LOCALES.AbstractTHE EFFECT OF THE SPATIAL DISPERSION OF A SEMICONDUCTOR FILM, HAVING A ROUGH FREE SURFACE AND OVERLYING A METAL, ON THE DIFFERENTIAL REFLECTION COEFFICIENT IS INVESTIGATED THEORETICALLY. THE INVESTIGATION IS CARRIED OUT NEAR EXCITON RESONANCE WHERE THE NONLOCALITY IS STRONG AND LEADS TO THE GENERATION OF ADDITIONAL POLARITONIC WAVES. APPLYING A FIRST-ORDER PERTURBATION THEORY, WE CALCULATE THE ANGULAR AND FREQUENCY DEPENDENCIES OF THE DIFFERENTIAL REFLECTION COEFFICIENT FOR THE CASE OF ONE-DIMENSIONAL ROUGHNESS. THE SPECTRA OF DIFFUSE REFLECTION FOR CUCL ON A AL METAL FOR INCIDENT LIGHT WITH S-POLARIZATION EXHIBIT PRONOUNCED RESONANCES (PEAKS) AT FREQUENCIES SATISFYING FABRY-PEROT CONDITIONS FOR THE ADDITIONAL POLARITONIC MODES. THESE CONDITIONS ALSO CORRESPOND TO THE SIZE QUANTIZATION OF THE EXCITON´S TRANSLATIONAL MOTION. OUR RESULTS SHOW THE USEFULNESS OF THE SPECTRA OF DIFFUSE REFLECTION FOR STUDYING THE EXCITATION OF QUANTIZED POLARITONIC MODES IN NONLOCAL FILMS.THE EFFECT OF THE SPATIAL DISPERSION OF A SEMICONDUCTOR FILM, HAVING A ROUGH FREE SURFACE AND OVERLYING A METAL, ON THE DIFFERENTIAL REFLECTION COEFFICIENT IS INVESTIGATED THEORETICALLY. THE INVESTIGATION IS CARRIED OUT NEAR EXCITON RESONANCE WHERE THE NONLOCALITY IS STRONG AND LEADS TO THE GENERATION OF ADDITIONAL POLARITONIC WAVES. APPLYING A FIRST-ORDER PERTURBATION THEORY, WE CALCULATE THE ANGULAR AND FREQUENCY DEPENDENCIES OF THE DIFFERENTIAL REFLECTION COEFFICIENT FOR THE CASE OF ONE-DIMENSIONAL ROUGHNESS. THE SPECTRA OF DIFFUSE REFLECTION FOR CUCL ON A AL METAL FOR INCIDENT LIGHT WITH S-POLARIZATION EXHIBIT PRONOUNCED RESONANCES (PEAKS) AT FREQUENCIES SATISFYING FABRY-PEROT CONDITIONS FOR THE ADDITIONAL POLARITONIC MODES. THESE CONDITIONS ALSO CORRESPOND TO THE SIZE QUANTIZATION OF THE EXCITON'S TRANSLATIONAL MOTION. OUR RESULTS SHOW THE USEFULNESS OF THE SPECTRA OF DIFFUSE REFLECTION FOR STUDYING THE EXCITATION OF QUANTIZED POLARITONIC MODES IN NONLOCAL FILMS.