WO2018169517A1

WO2018169517A1 - Terahertz-gigahertz illuminator

Info

Publication number: WO2018169517A1
Application number: PCT/US2017/022267
Authority: WO
Inventors: Lawrence Dah-Ching TZUANG; Yen-Ju Wu
Original assignee: Archit Lens Technology Inc.
Priority date: 2017-03-14
Filing date: 2017-03-14
Publication date: 2018-09-20

Abstract

Terahertz-gigahertz illuminator that may be implemented in or attached to many gigahertz/ terahertz applications or systems (such as imaging, security or communication system) is proposed. One or more THz emitters are combined to form an array, where each THz emitter is comprised of a THz source and a THz lens. Furthermore, for each THz emitter, the geometric relation between the THz source and the THz lens may be dynamically configured to adjust the emission angle and/or the pointing angle of the launched THz wave. In addition, each THz emitter may be rotated to adjust the pointing angle of the launched THz wave. Therefore, the THz illuminator may uniformly illuminate the object of different sizes at different distances while maximizing the effective illumination without configuring other aspects of the THz source. In this way, the effective use of the limited THz source power provided by each individual THz emitter is achieved.

Description

TERAHERTZ-GIGAHERTZ ILLUMINATOR

FIELD OF THE INVENTION

[0001] The present invention relates to the terahertz-gigahertz (THz) illuminator, especially to the THz illuminator capable of maximizing the effective illumination on the subject, while improving its uniformity.

BACKGROUND OF THE INVENTION

[0002] The interest in THz technology has significantly increased during the past decades, and the commercial applications utilizing THz systems have stably increased as well. For example, both the THz imaging system and the THz security system have valuable commercial values because of its unique THz wave transmission properties. One classic example is the identification of concealed objects, such as a metal weapon hidden under a fiber cloth. Furthermore, due to the high frequency of the THz waves compared to radio-frequencies, high bandwidth data carried by THz wave may enable future generations of communication systems.

[0003] The development of the THz technology has to confront some critical challenges. One such challenge is that the commercial THz sources that are currently available are both relatively low power and expensive. For example, the output power of commercial THz sources are typically in the tens of milli-watt range, which is significantly lower than moderate performing light-emitting-diodes (LEDs) or even household light bulbs. Hence, the designs and the applications of the THz system are clearly limited by the capability of the THz source. Furthermore, since the

THz wave is not visible, how to maximize the effective illumination and to improve uniformity of the THz wave shined on one or more objects at any distance, is a difficult problem, especially if one or more objects and one or more THz sources are existed. To make matters more complicated, the geometric relations between the objects and the THz sources can be constantly varying.

[0004] Therefore, it is required to provide a terahertz-gigahertz illuminator capable of dynamically maximizing the effective illumination, while at the same time improving the uniformity of the illumination.

SUMMARY OF THE IVENTION

[0005] The proposed invention of the terahertz-gigahertz illuminator (THz illuminator) uses one or more proposed THz emitters arranged in an array. Furthermore, the configuration within each proposed THz emitter is dynamically configurable.

[0006] Essentially, the proposed THz emitter is composed of a THz source and a THz lens. In additional, a fixture is configured to hold both the THz source and the THz lens together. The THz source may be any well-known, on-developed or to-be-appeared THz source. The THz lens may be a single lens element or a set of lens elements that possess THz wave converging power. For some examples, the THz source is placed on or near to the focal point of the THz lens such that the THz wave generated by the THz source will emit on the opposite side. The focal length of the THz lens should be small to allow the THz lens to collect as much THz wave as possible. For some examples, the THz source and/ or the THz lens may be translated along the geometrical axis, defined as the line that crosses the geometric centers of both the THz lens and the THz source, so as to adjust the emission angle of the THz wave passing through the THz lens. For some examples, the THz source and/ or the THz lens may be translated along a direction vertical to and/ or intersecting the geometrical axis so as to adjust the pointing angle of the THz wave launched from the THz emitter. For some examples, the THz source and/ or the THz lens may be rotated, such as around a direction intersecting the geometrical axis, so as to adjust the pointing angle of the launched THz wave. Herein, the emission angle is defined as the angular range of the THz wave launched from the THz emitter, and the pointing angle is defined as the angle between the center of the angular range and the geometrical axis.

[0007] Essentially, the distributions of the THz emitters may be a single point (i.e., a zero-dimensional array), a one-dimensional array, a two- dimensional array, a three-dimensional array or others. For example, the THz emitters may be placed along a straight line, a curve or a zigzag. For example, the THz emitters may be distributed on a square, a circle, a polygon, a planar surface, a curved surface or an undulant surface. For example, the THz emitters may be distributed as a two-dimensional array on a plane but at least two THz emitters having different amount of shifts along a direction intersecting or vertical to the plane. For example, the THz emitters may be regularly distributed or equally spaced for achieving better illumination uniformity.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1A briefly illustrates a THz illuminator having some similar

THz emitters, FIG. IB briefly illustrates the configuration of the THZ emitter, FIG. 1C and FIG. ID define the emission angle and the pointing angle of the THz wave launched by the THz emitter, respectively, and FIG. IE to FIG. IF briefly illustrate some THz emitters having the internal driver or external driver, respectively.

[0009] FIG. 2A and FIG. 2B briefly illustrate a THz illuminator having only one THZ emitter arranged in a zero-dimensional array, and FIG. 2C and FIG. 2D briefly illustrate that the distance between the THz source and the THz lens is dynamically configured through using an internal driver inside the THz emitter to dynamically adjust the emission angle for maximizing the effective illumination.

[OOIO] FIG. 3A and FIG. 3B briefly illustrate a THz illuminator having some similar THZ emitters arranged in a one-dimensional array wherein the emission angle for each THz emitter is adjusted according to the object distance, and FIG. 3C and FIG. 3D present the illumination pattern and the relation between the emission angle and the object distance according to an example having four THz emitters, each with 1 Watt of power arranged in a one-dimensional array with a period of 40 cm.

[0011] FIG. 4A and FIG. 4B briefly illustrate a THz illuminator having some similar THz emitters arranged in a one-dimensional array wherein each of the THz emitter may dynamically adjust both its pointing angle and/ or emission angle, and FIG. 4C briefly presents the emission angle versus both the object distance and the object dimension when the THz emitters are equally spaced in an array but each THz emitter should have a specifically configured pointing angle.

[0012] FIG. 5A briefly illustrates a THz illuminator having three similar THz emitters arranged in a one-dimensional array, and FIG. 5B to FIG. 5F briefly show how the three THz emitters are dynamically configured according to these mentioned steps.

[0013] FIG. 6 briefly illustrates the front view and the side view of a THz illuminator having sixteen THz emitters arranged in a 4x4 array, wherein these THz emitters are embedded in a common panel.

DETAILED DESCRIPTION OF THE INVENTION [0014] Reference will now be made in details to specific embodiment of the present invention. Examples of these embodiments are illustrated in the accompanying drawings. While the invention will be described in conjunction with these specific embodiments, it will be understood that the intent is not to limit the invention to these embodiments. In fact, it is intended to cover alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. The present invention may be practiced without at least one of these specific details. In other instances, the well-known portions are less or not described in detail in order not to obscure the present invention.

[0015] The proposed THz illuminator has one or more THz emitters and uses the THz waves launched from all the THz emitters collectively, wherein the THz emitters may be dynamically configured independently according to the positions and sizes of the objects to be illuminated. Herein, FIG. 1A briefly illustrates the situation that a THz illuminator 100 having some similar (even identical) THz emitters 1 10. As briefly illustrated in FIG. IB, each THz emitter 1 10 has a THz source 1 12 and a THz lens 1 14, wherein the THz source 1 12 is placed on or near to the focal point of the THz lens 1 14. Both the emission angle and the pointing angle of the launched THz wave are defined in FIG 1C and FIG. ID. FIG. 1C shows the situation that the launched THz wave 199 is propagating along the geometrical axis, which is defined as the line crosses the geometric centers of both the THz lens 1 14 and the THz source 1 12, which means that the pointing angle (defined as the angle between the center of the angular range and the geometrical axis) is zero. FIG. ID shows the situation that the launched THz wave 199 is propagating along a propagation direction intersecting the geometrical axis, which gives a nonzero pointing angle because emission angle is symmetric with the propagating direction. As shown in FIG. IE, for each THz emitter 1 10, an internal driver 1 16 may be used to translate and/or rotate the THz lens 1 14 and/or the THz source 1 12. In particular, to rotate the THz lens 1 14, the rotation axis is usually vertical to the geometrical axis of the THz lens 1 14. In another example, as shown in FIG. IF, for each THz emitter 1 10, an external driver 1 18 may be used to rotate the entire THz emitter 1 10. Significantly, by using the internal driver 1 16 and/or the external driver 1 18, for each THz emitter 1 10, the emission angle and/or the pointing angle of the launched THZ wave 199 may be dynamically configured.

[0016] In general, the THz lens 1 14 can be a single lens element or a set of lens elements, and the THz source 1 12 is placed on or near the focal point of the THz lens 1 14 such that the THz wave generated by the THz source 1 12 will emit on the opposite side. Thus, the THz wave generated by the THz source 1 12 will transmit through the THz lens 1 14 and then will illuminate an object with a finite size at a finite distance on the opposite side. Moreover, to avoid diffraction and to ensure that small emission angle can be achieved, the diameter of the THz lens 1 14 usually is at least 5 to 10 times of the wavelength of the THz wave generated by the THz source. For example, if the THz illuminator 100 is designed for the THz wave with frequency at 100 GHz, a 30 mm minimum lens diameter is preferred. For example, a 10 times ratio will result in a minimum emission angle not only limited by diffraction, but also depending on the focal length of the THz lens 1 14. However, a larger diameter of THz lens 1 14 may be disadvantageous because of the material cost, size, and weight. Moreover, the thickness of the THz lens 1 14 is not limited, although a thinner THz lens 1 14 is preferred because of lower material cost, less THz wave absorption, and ease of manufacturing.

[0017] Furthermore, the performance of the THz lens 1 14 may be similar with the performance of at least one of the following: a plano-convex lens, a plano-concave lens, a convex-convex lens and a convex-concave lens. Besides, for each lens element, one or more non-planar surfaces may be spherical or aspherical, although aspherical surface may be more useful for reducing the lens thickness and weight.

[0018] Some embodiments of the proposed invention are briefly illustrated in FIG. 2A to FIG. 2D and relates to the THz illuminator 200 having only one THz emitter 210 (or viewed as a zero-dimensional array) with a fixed pointing angle. In these embodiments, if the distance between the THz source 212 and the THz lens 214 is fixed, the emission angle of the launched THz wave 299 is fixed accordingly. Thus, the launched THz wave 299 may not properly illuminate the object 251/253 if the size of object 251/253 is different than the beam width of the launched THz wave 299 arriving at object 251/253. However, by using the internal driver 216 to configure the geometric relation, such as the distance, between the THz lens 214 and the THz source 212, these embodiments may dynamically configure the emission angle of the launched THz wave 299 (or viewed as may configure the beam width of the launched THz wave 299 shined on objects 251/253) to cover the entire object 251/253. Hence, partial illumination on object 251/253 is mitigated. In summary, these embodiments may maximize the effective illumination of the THz wave 299 generated by the THz source 212 to illuminate the objects 251/253 properly.

[0019] Some embodiments of the proposed invention are briefly illustrated in FIG. 3A and FIG. 3B and relate to the THz illuminator 300 having some same (even identical) THz emitters 3 10 with fixed pointing angle and arranged in an equally-spaced one-dimensional array. In these embodiments, to both efficiently use the individual THz emitters 3 10 and to uniformly illuminate the object 35 at any distance from the THz illuminator 300, these THZ emitters 3 10, when operating collectively, should have a particular and similar emission angles of the launched THz wave such that the area of the illumination remains constant at about the size of the array for any object distances. For example, by assuming each THz emitter 3 10 emits the THz waves 399 with a Gaussian profile, each THz emitter 3 10 may have an emission angle which is defined as 2*tan^~ ¹(0.5*period/ (object distance)), wherein the period is defined as the spacing of the THz emitter array 300. In other words, whenever the object distance is determined, all THz emitters 3 10 may be dynamically configured to have the required emission angle of the launched THz wave 399 to uniformly illuminate the object. To provide a specific example, if the emission angle for all the THz emitters 3 10 are dynamically configured correctly, the illumination pattern of four THz emitters 3 10, each having 1 W (one Walt) of power, arranged in a straight line with a period of 40 cm is shown in FIG. 3C. Furthermore, as shown in FIG. 3D, the illumination profile is uniform at the object plane, also the emission angle of each THz emitter is varied accordingly depending on the object distance. In summary, the internal driver may be used to dynamically configure the distance between the THz source 3 12 and the THz lens 3 14 according to the object distance.

[0020] Some embodiments of the proposed invention are briefly illustrated in FIG. 4A and FIG. 4B and relate to the THz illuminator 400 having some similar THz emitters 410 arranged in a one-dimensional array. Herein, FIG. 4A illustrates the situation that the object 451 is positioned away from the THz emitters 410 and not directly in front (on the side) of the THz illuminator 400, and FIG. 4B illustrates the situation that the objects 452/453 are positioned near to the THz emitters 410 and are directly in front of the THz illuminator 400. In these embodiments, each of the THz emitters 410 may dynamically adjust both its pointing angle and emission angle when needed. When in action, the THz emitters 410 may collectively illuminate the objects 451/452/453 of any size, at any object distance, and even for objects that are not directly in front of the THz illuminator 400. Clearly, by dynamically configuring both the pointing angle and the emission angle of each THz emitter 410 in a particular combination, the THz wave 499 launched from all the dynamically configured THz emitters 410 covers, and only covers, objects 451/452/453. Herein, for each THz emitter 410, the emission angle is smaller and the pointing angle is larger in the previous situation, but the emission angle is larger and the pointing angle is smaller in the latter situation. Furthermore, by assuming each THz emitter 410 is equally spaced and emits THz waves 499 with a Gaussian profile, each THz emitter 410 may have the emission angle defined as 2*tan ¹(0.5*FWHM/ (object distance)), wherein the FWHM is the full-width-half-max of the illumination on the object. To uniformly illuminate the object using all THz emitters 410 collectively, the FWHM equals to the desired area of illumination (object dimension) divided by the axial number of the THz emitters 410 (ANOS). For each individual THz emitter 410, to adjust the pointing angle, an internal driver may be used to configure the relative position between the THz source and the THz lens. The internal driver may also be used to rotate and/or translate the THZ lens and/or the THz source, even an external driver may be used to rotate the entire THz emitter 410, to dynamically adjust the pointing angle. For the Xth row (or column) of the THz emitter 410 in the THz illuminator 400, the pointing angle is defined as the object angle plus tan ¹ (((array period)*(0.5*(ANOS)- l)-X)/ ((FWHW)*(0.5*(ANOS)- 1)-X)), wherein the object angle is the angle between the geometrical axis and the direction connecting the THz lens to the illuminated object. To describe further, FIG. 4C shows the emission angle for each of the THz emitter 410 with respect to a given object distance and object dimension combination. For this particular example shown in FIG. 4C, the calculation assumes 1) the pointing angle is specifically chosen based on the above equation, and 2) the period of the THz illuminator 400 (spacing for all THz emitters) is 40 cm.

[0021] Significantly, as mentioned in all the aforementioned embodiments, the invention has two key features. First, for each THz emitter, the geometric relation between the THz source and the THz lens is dynamically configurable such that the emission angle and/ or the pointing angle of the launched THz wave may be adjusted. Second, for some THz emitters arranged in an array, different THz emitters may be dynamically configured independently such that the THz waves launched together from these THz emitters may be shaped in a way that provide effective and uniform illumination on the object(s) of different size and location(s). Accordingly, the invention does not limit other details if the two key features mentioned above can be achieved.

[0022] For example, for each THz emitter, the geometric relation between the THz source and the THz lens may be configured by at least one of the following steps: translating the THz source along the geometrical axis, translating the THz lens along the geometrical axis, translating the THz source along a direction vertical to or intersecting the geometrical axis, translating the THz lens along a direction vertical to or intersecting the geometrical axis, rotating the THz lens around a direction vertical to or intersecting the geometrical axis, and rotating the THz source around a direction vertical to or intersecting the geometrical axis. For example, for these THz emitters arranged in an array, both the pointing angle and the emission angle of the THz waves launched from these THz emitters may be dynamically configured by at least one of the following steps: freely rotating at least one THz emitter without changing the geometric relation between the THz source and the THz lens inside the rotated THz emitter, freely translating at least one THz emitter without changing the geometric relation between the THz source and the THz lens inside the translated THz emitter, and changing the geometric relation between the THz source and the THz lens inside at least one THz emitter. Just for examples, FIG. 5A briefly illustrate a THz illuminator having three THz emitters arranged in a one-dimensional array, and FIG. 5B to FIG. 5F briefly illustrate how the three THz emitters are dynamically configured according to these steps mentioned above respectively. Herein, the THz illuminator is labeled as 500, the THz emitter is labeled as 510, the THz source is labeled as 512, and the THz lens is labeled as 514.

[0023] As a short summary, for each THz emitter 510, the emission angle of the launched THz wave may be modified by one or more of the following: translate the THz lens 514 along the geometrical axis and translate the THz source 512 along the geometrical axis. Further, the pointing angle of the launched THz wave may be modified by one of more of the following: rotate the THz lens 514 around a direction vertical to or intersecting the geometrical axis, rotate the THz source 5 12 around a direction vertical to or intersecting the geometrical axis, translate the THz lens 514 along a direction vertical to or intersecting the geometrical axis, translate the THz source 512 along a direction vertical to or intersecting the geometrical axis, and rotate the THz emitter 510 around a direction vertical to or intersecting the geometrical axis.

[0024] Further, in general, the rotation angle is equal to or smaller than 45 degrees to ensure that most THz waves launched from the THz source transmit through the THz lens 514. On a similar note, in general, the distance between the THz source 512 and the THz lens 514 is equal to or smaller than the focal length (or the effective focal length) of the THz lens 514 to ensure that most of the THz waves launched from the THz source 512 may transmit through the THz lens 514. In several examples, the internal driver may be designed to translate the THz lens along the geometrical axis or a direction intersecting or vertical to the geometrical axis, wherein the distance between the THz lens and the THz source along the geometrical axis is maintained to be equal to or smaller than the diameter of the THz lens. In several examples, the internal driver may be designed to translate the THz source along the geometrical axis or a direction intersecting or vertical to the geometrical axis, wherein the distance between the THz lens and the THz source along the geometrical axis is maintained to be equal to or smaller than the diameter of the THz lens. In several examples, the internal driver may be configured to rotate the THz lens around a direction intersecting or vertical to the geometrical axis wherein the rotation angle is equal to or small than 45 degrees. Also, in several examples, the internal driver may be configured to rotate the THz source around a direction intersecting or vertical to the geometrical axis wherein the rotation angle is equal to or small than 45 degrees. Again, in several examples, the external driver may also be configured to rotate the THz emitter around a direction intersecting or vertical to the geometrical axis wherein the rotation angle is equal to or smaller than 45 degrees.

[0025] Furthermore, although only zero-dimensional and one-dimensional arrays are illustrated in the above embodiments, the invention may also arrange a plurality of THz emitters in a two-dimensional array or a three- dimensional array. Furthermore, the details of the array are not limited. For example, the zero-dimensional array is a single point, which means only one THz emitter is used. For example, if two or more THz emitters are used, the one-dimensional array may be a straight line, a curve or a zigzag. For example, if three or more THz emitters are used, the two-dimensional array may be a square, a circle, a polygon, a planar surface, a curved surface, a smooth surface or an undulant surface. For example, for the three-dimensional array, four or more THz emitters may be distributed as the two-dimensional array discussed above on a plane but at least two of those THz emitters have different amount of shifts along a direction intersecting or vertical to the plane. Furthermore, it is beneficial, but not mandatory, to place the THz emitter(s) in equal spacing. Herein, FIG. 6 briefly illustrates the front view and the side view of a THz illuminator having sixteen THz emitters arranged in a two-dimensional 4x4 array, wherein these THz emitters are embedded in a common panel.

[0026] One of the advantages of the proposed THz illuminator is that the required size of the THz lens is reasonably small because each THz source pairs with an independent THz lens. Due to the poor power performance for the THz sources, the usage of multiple THz sources could become prevalent in the near future. In addition, using a number of small THz lenses can be potentially cheaper and lighter than the usage of a few large THz lenses to control the THz illumination.

[0027] In addition, to minimize the size for providing a compact and portable THz illuminator, each THz emitter may be immediately adjacent to the neighboring THz emitter(s). Also, to match the pre-determined illuminator's operation environment or to match the potential distribution range of the size(s) and the position(s) of the object(s), it is at times beneficial that each THz emitter is separated from other THz emitters.

[0028] Furthermore, the material of the THz lens (or viewed as the material of each lens element) may be glass, quartz, or any other material being transparent for the THz wave. Besides, the details of both the internal driver and the external driver are not limited, too. For example, a combination of motor(s) and mechanical part(s)/structure(s) may be used to translate and/ or rotate the THz source and/ or the THz lens, and a rotary actuator may be used to rotate the entire THz emitter. In addition, to further improve the transmission of the THz wave launched from the THz emitter, it is optional that at least a portion of the THz lens is coated by an anti-reflection layer or at least a portion of one or more lens elements are coated by an anti-reflection layer. It is also optional that at least a portion of the surface of the fixture for holding both the THz lens and the THz source is coated (or covered) by an anti-reflecting absorbing layer. Herein, the anti-reflecting absorbing layer may be made of any material capable of both absorbing the THz wave and minimizing reflection of the THz wave launched from the THz source. Just for example, the anti- reflection absorbing layer may be made of Expandable Polypropylene (EPP) doped with carbon particles, sliver particles, or other conductive particles.

[0029] Although the embodiments described above use one or more similar THz emitters collectively to build the THz illuminator, the proposed invention may also use identical or different THz emitters to build the THz illuminator. In other words, the proposed invention may use different THz emitters having different THz lenses and/ or different THz sources, although the THz illuminator built by different THz emitters usually is more complex than the THz illuminators built by identical THz emitters. For example, different THz emitters having different THz lens may require different geometric relations between the THz lens and the THz source to obtain similar (even identical) emission or pointing angle for each of the THz emitters.

[0030] The applications of the proposed THz illuminator may be briefly described below. In the case that the THz illuminator is embedded in a THz imaging system, a device that detects the object's distance (for example, a depth imager or a radar system) and a THz illuminator may be used together. The role of the depth imager or a radar system is to find the position of the object of interest. Then, the THz illuminator reacts accordingly such that the THz waves may focus on the object of interest such that it uniformly and effectively illuminates on only the object of interest. This way results in improved signal-to-noise-ratio of the THz imaging system.

[0031] The presently disclosed embodiments should be considered in all respects to be illustrative and not restrictive. The scope of the invention is indicated by the appended claims rather than the foregoing description, and all variation which come within the meaning and range of equivalents thereof are intended to be embraced therein.

Claims

What is claimed is:

1. A terahertz-gigahertz illuminator, comprising:

a THz emitter having a THz source and a THz lens;

wherein the emission angle and/ or the pointing angle of the THz wave launched by the emitter are dynamically configurable;

wherein the emission angle is defined as the angular range of the

THz wave launched from the THz emitter;

wherein the pointing angle is defined as the angle between the center of the angular range and the geometrical axis, where the geometrical axis is defined as the line that crosses the geometric centers of both the THz lens and the THz source.

2. The terahertz-gigahertz illuminator as claimed in claim 1, wherein the diameter of the THz lens is at least five to ten times of the wavelength of the THz wave generated by the THz source.

3. The terahertz-gigahertz illuminator as claimed in claim 1, wherein the THz lens is a single lens element or a combination of multiple lens elements.

4. The terahertz-gigahertz illuminator as claimed in claim 3, wherein one or more the non-planar surfaces of the lens elements are spherical or aspherical.

5. The terahertz-gigahertz illuminator as claimed in claim 3, wherein the performance the THz lens is similar with the performance of at least one of the following: a plano-convex lens, a plano-concave lens, a convex-convex lens and a convex-concave lens.

6. The terahertz-gigahertz illuminator as claimed in claim 1, wherein the THz source is placed on or near the focal point of the THz lens.

7. The terahertz-gigahertz illuminator as claimed in claim 1, further comprising at least one of the following:

an internal driver configured to translate the THz source along the geometrical axis; and

an internal driver configured to translate the THz lens along the geometrical axis.

8. The terahertz-gigahertz illuminator as claimed in claim 1, further comprising at least one of the following:

an internal driver configured to rotate the THz lens; and

an internal driver configured to rotate the THz source.

9. The terahertz-gigahertz illuminator as claimed in claim 1, further comprising an external driver configured to rotate the entire THz emitter without changing the geometric relation between the THz source and the THz lens.

10. The terahertz-gigahertz illuminator as claimed in claim 7 or 8 or 9, further comprising at least one of the following:

the internal driver is configured to translate the THz lens along the geometrical axis wherein the distance between the THz lens and the THz source is maintained to be equal to or smaller than the diameter of the THz lens;

the internal driver is configured to translate the THz lens along a direction intersecting the geometrical axis wherein the distance between the THz lens and the THz source is maintained to be equal to or smaller than the diameter of the THz lens;

the internal driver is configured to translate the THz source along the geometrical axis wherein the distance between the THz lens and the THz source is maintained to be equal to or smaller than the diameter of the THz lens;

the internal driver is configured to translate the THz source along a direction intersecting the geometrical axis wherein the distance between the THz lens and the THz source is maintained to be equal to or smaller than the diameter of the THz lens;

the internal driver is configured to rotate the THz lens around a direction intersecting the geometrical axis of the THz lens, wherein the rotation angle is equal to or small than 45 degrees;

the internal driver is configured to rotate the THz lens around a direction vertical to the geometrical axis of the THz lens, wherein the rotation angle is equal to or smaller than 45 degrees;

the internal driver is configured to rotate the THz source around a direction intersecting the geometrical axis of the THz lens, wherein the rotation angle is equal to or smaller than 45 degrees;

the internal driver is configured to rotate the THz source around a direction vertical to the geometrical axis of the THz lens, wherein the rotation angle is equal to or smaller than 45 degrees;

the external driver is configured to rotate the THz emitter around a direction intersecting the geometrical axis of the THz lens, wherein the rotation angle is equal to or smaller than 45 degrees; and

the external driver is configured to rotate the THz emitter around a direction vertical to the geometrical axis of the THz lens, wherein the rotation angle is equal to or smaller than 45 degrees.

1 1. The terahertz-gigahertz illuminator as claimed in claim 1 , further comprising at least one of the following:

one or more lens element(s) of the THz lens is coated by an anti- reflection layer; and

at least a portion of the inner surface of a fixture for holding both the THz lens and the THz source is formed, coated, or covered by an anti- reflecting absorbing layer.

12. The terahertz-gigahertz illuminator as claimed in claim 1, further comprising two or more THz emitters placed on a one-dimensional array.

13. The terahertz-gigahertz illuminator as claimed in claim 12, wherein the one-dimensional array is chosen from a group of the following: a straight line, a curve, or a zigzag.

14. The terahertz-gigahertz illuminator as claimed in claim 1, further comprising some THz emitters placed on a two-dimensional array or a three-dimensional array.

15. The terahertz-gigahertz line as claimed in claim 14, wherein the two- dimensional array is chosen from a group of the following: a circle, a polygon, a planar surface, a curved surface, and an undulant surface.

16. The terahertz-gigahertz illuminator as claimed in claim 12 or 14, wherein the individual THz emitters may be configured to emit THz waves with specific emission angles and specific pointing angles.

17. The terahertz-gigahertz illuminator as claimed in claim 12 or 14, further comprising at least one of the following:

at least two THz emitters may be dynamically configured to emit THz waves with different emission angles; and

at least two THz emitters may be dynamically configured to emit THz waves with different pointing angles.

18. The terahertz-gigahertz illuminator as claimed in claim 12 or 14, further comprising at least one of the following: some similar THz emitters are arranged in an array;

some identical THz emitters are arranged in an array; and

some different THz emitters are arranged in an array.

19. The terahertz-gigahertz illuminator as claimed in claim 12 or 14, further comprises at least one of following:

at least one THz emitter may be freely rotated;

at least one THz emitter may be freely translated; and

at least two THz emitters may dynamically configure the emission angle and/or the pointing angle of the launched THz waves.

20. The terahertz-gigahertz illuminator as claimed in 12 or 14, further comprising at least one of the following:

the THz emitters are regularly distributed over the entire array; and the THz emitters are equally spaced over the entire array.