SE ANALIZA TEÓRICAMENTE LA ABSORCIÓN DE DOS FOTONES DENTRO DEL FORMALISMO SEMICLÁSICO DE LA INTERACCIÓN ENTRE LA RADIACIÓN Y LA MATERIA. CONSIDERAMOS UN CONJUNTO, CON ENSANCHAMIENTO INHOMOGÉNEO, DE ÁTOMOS DE TRES NIVELES SOMETIDO A LA ACCIÓN DE DOS CAMPOS CONTRAPROPAGANTES DE IGUAL FREQUENCIA. RESOLVEMOS PERTURBATIVAMENTE LAS ECUACIONES DE BLOCH DEL SISTEMA DE UNA FORMA NO USUAL CONCENTRÁNDONOS EN EL LÍMITE DE ALTA DESINTONÍA DE LAS TRANSICIONES A UN FOTÓN. DE ESTA FORMA OBTENEMOS UNA EXPRESIÓN ANALÍTICA PARA LA ANCHURA DE LA RESONANCIA A DOS FOTONES EN LA QUE SE PONE DE MANIFIESTO LA POSIBILIDAD DE ESPECTROSCOPIA SUB”DOPPLER A DOS FOTONES. TAMBIÉN OBTENEMOS UNA EXPRESIÓN ANALÍTICA PARA EL DESPLAZAMIENTO STARK DE LA RESONANCIA A DOS FOTONES.AbstractTWO PHOTON ABSORPTION IS THEORETICALLY ANALYZED WITHIN THE SEMICLASSICAL FORMALISM OF RADIATION MATTER INTERACTION. WE CONSIDER AN ENSEMBLE OF INHOMOGENEOUSLY BROADENED THREE LEVEL ATOMS SUBJECTED TO THE ACTION OF TWO COUNTERPROPAGATING FIELDS OF THE SAME FREQUENCY. BY CONCENTRATING IN THE LIMIT OF LARGE DETUNING IN ONE PHOTON TRANSITIONS, WE SOLVE PERTURBATIVELY THE BLOCH EQUATIONS IN A NON-USUAL WAY. IN THIS WAY WE DERIVE AN ANALYTICAL EXPRESSION FOR THE WIDTH OF THE TWO PHOTON RESONANCE THAT MAKES EVIDENT SUB-DOPPLER TWO PHOTON SPECTROSCOPY. WE ALSO DERIVE AN ANALYTICAL EXPRESSION FOR THE STARK SHIFT OF THE TWO PHOTON RESONANCE.TWO PHOTON ABSORPTION IS THEORETICALLY ANALYZED WITHIN THE SEMICLASSICAL FORMALISM OF RADIATION MATTER INTERACTION. WE CONSIDER AN ENSEMBLE OF INHOMOGENEOUSLY BROADENED THREE LEVEL ATOMS SUBJECTED TO THE ACTION OF TWO COUNTERPROPAGATING FIELDS OF THE SAME FREQUENCY. BY CONCENTRATING IN THE LIMIT OF LARGE DETUNING IN ONE PHOTON TRANSITIONS, WE SOLVE PERTURBATIVELY THE BLOCH EQUATIONS IN A NON-USUAL WAY. IN THIS WAY WE DERIVE AN ANALYTICAL EXPRESSION FOR THE WIDTH OF THE TWO PHOTON RESONANCE THAT MAKES EVIDENT SUB-DOPPLER TWO PHOTON SPECTROSCOPY. WE ALSO DERIVE AN ANALYTICAL EXPRESSION FOR THE STARK SHIFT OF THE TWO PHOTON RESONANCE.