Patent GB-1089453-A (GB)
Title: Improvements in or relating to apparatus employing semiconductor crystals for producig or amplifying electromagnetic radiation
IPC: H01S3/109
Filed: 1964-08-28
Abstract: 1,089,453. Masers. SIEMENS A.G. Aug. 28, 1964 [Aug. 30, 1963], No. 35263/64. Heading H1C. [Also in Divisions H3 and H4] Radiation at light or microwave frequencies is generated or amplified by irradiating successive semi-conductors, the atomic components of which have been excited to higher energy levels, e.g. thermally, electrically, magnetically or ultrasonically. An irradiated first crystal produces as one of its scatter (secondary) radiation frequencies the sum or difference (depending on the energy level(s) excited) of the incident frequency and a characteristic frequency corresponding to a quantum level difference of the crystal and this combination frequency is applied to the next crystal stage to produce a further frequency change and so on. Scatter radiation of the incident frequency is. also produced in each crystal and may be coherent or non-coherent dependent on the incident frequency. Such coherent radiation may be used for amplification and the incoherent radiation so produced may be used to excite other crystals. The combination frequency produced in one stage may be equal to, or a multiple or submultiple of a characteristic frequency of an adjacent stage. The crystals may be enclosed in housings with permeable apertures for input and output radiation; or may be in the form of thin films between adjacent stages; or may be separated by layers having polarizing, birefringent or reflecting properties at particular frequencies. They may be separated by acoustically reflecting material, if energized separately by ultrasonic inputs. The crystals may be of covalent (homopolar) or ionic type, or monocrystalline with paramagnetic or feromagnetic impurity ions whose spin frequencies are equal to the combination frequencies of other stages; or may be molecular with Van der Waal bonding e.g. organic type. Feedback may be used from one crystal to a previous one to enhance the amplification. A crystal may also be piezo-electric so that its quantum energy levels may be varied by force applied to a point or edge, or by a clamp. In Figs. 9-11, the (input) Fig. 9 system changes the irradiating frequency V to a value V 9  used for pumping a second stage, Fig. 11, with paramagnetic ions in the crystal lattice and the irradiating input frequency V is also applied to a third stage, Fig. 10, similar to that of Fig. 9 but with its crystal compressed or subjected to a strong electric field so that its quantum energy levels differ slightly from the first stage, and a different frequency output V10 is obtained from the third stage, Fig. 10, which exactly equals one of the relatively low frequencies corresponding to and produced from the pumped second stage and therefore the third stage output is amplified Maser-wise by the pumped second stage. The amplified coherent output hV10 and also that of the third stage, may then be applied to a fourth crystal stage, Fig. 12, compressed so that its radiation frequency output may equal that of the incident radiation on the first stage, or the pumping frequency. In Figs. 13-16 (not shown) four crystals with equally decreasing energy gaps, produced by deformation, are used, and the relatively lowfrequency (V 6 ) corresponding to the staircase decrease in energy level is amplified. Each stage has incident on it not only the frequency output (V 6 ) of the preceding stage but also the frequency output V 6  of earlier stages. Moreover feedback at a different frequency is employed from each stage to the preceding one to increase the quantum level excitations. The fourth and final stage comprises several crystals producing multiple reflections of the output coherent frequency (V 6 ). The crystals stages may be successively heated to higher temperatures. The amplifying system may be used as a frequency converter, a filter, a sideband amplifier, or image converter, or as a compact radiation therapy probe. The output may be modulated by mechanical, electric or magnetic force applied to one or more crystals. The frequencies may range from microwave, to visible or ultra-violet, and the output may be of much reduced frequency or of higher frequency relative to the input.