High-capacity and security molecular capsule transporters

Abstract

Multiwavelength optical capsules can be generated and controlled by using soliton/Gaussian pulses within a nonlinear device system known as a “PANDA” ring circuit and system. The security of molecule/drug transportation can be formed by the strong coupling of soliton-like pulse, where the high-capacity optical capsules can be formed using the multiwavelength solitons, which can be a good advantage and combination of drug delivery to the required targets. Moreover, the multiple access of drug delivery can be formed using the optical networks, which allows the use of various drug molecules with variety of diagnosis and therapeutic applications.

Keywords::

• high-capacity transporter
• high-security transporter
• molecular transporter
• optical capsule

Introduction

Optical capsule has become the promising tool for molecule/substance trapping and transportation, which can be used for drug delivery and related various applications, in which the security function is the advantage. Recently, the use of optical capsule for drug delivery has been firstly reported by the authors in reference (Yupapin et al. 2013), where they have reported that optical capsules can be established by orthogonal soliton pairs, which are in fact they are the sum of wave vectors. These are the optical tweezers generated by orthogonal solitons (Ashkin and Dziedzic 1987, Sasaki et al. 1992, Kelemen et al. 2006, Keyser et al. 2006, Aziz et al. 2012a), where there are two forms, which one is the surface plasmon, the other is a potential well. The sum of wave vectors can produce the resulting force and move forward in the wave propagation direction into the medium, especially, optical waveguide, which means that this principle can be used for long-distance drug delivery. Moreover, the security transmission is the advantage of the scheme. However, the use of soliton in the system has brought the problem of system limitation, where the soliton generation system is always complicated and expensive, therefore, in this paper we have proposed the a simple soliton generation technique, which has been proposed by Tamee et al. (2013), which they have reported the use of an interesting system and results that can be used to form the multiwavelength solitons. The multicolor(multiwavelength) solitons are now easily generated and controlled using the Gaussian input pulse (common laser pulse) propagating within typical modified add-drop filter (Lundquist et al. 1998, Torner and Barthelemy 2003, Kato and Mori 2006, Aziz et al. 2012b, Assanto and Smyth 2013, Kartashov et al. 2013), in which two nonlinear devices are used incorporating the center ring known as a PANDA ring circuit (Uomwech et al. 2010). In operation, light from a common laser source with wide range of center wavelength is input into the system as shown in Figure 1. The nonlinear behavior of light propagation within the system is occurred by the coupling effects from the two nonlinear side rings, in which the four-wave mixing of light can be introduced within the system due to the superposition of the chaotic signals, which is generated by the two nonlinear side rings. Finally, the resonant situation of some wavelengths can be introduced and pumped the propagation modes, which can be seen at the system output port, where in this case the multiwavelength output signals are obtained, in which the two soliton properties (i) self-phase and (ii) cross-phase modulation without dispersion remain. To change the multiwavelength or color soliton bands, the use of the control port is required by inputting the moderated signal via the add port, in which multicolor solitons can be generated and controlled for various applications.

Figure 1. Multiwavelength soliton generation system, where E_i: optical fields; R_i: ring radii, R_ad: Add-drop ring radius, κ_i: coupling coefficients.

In this paper, the multi-wavelength optical capsules can be generated by controlling the orthogonal soliton pulses within a PANDA ring circuit and securely transported into the optical networks, which can be useful for molecule/substance trapping and transportation. There are three mesh networks, for instance tree, ring and star optical networks proposed in this works, where the network stability can be calculated and found in our previous works (Mitatha et al. 2011, Moongfangklang et al. 2011). The advantages of this system such as (i) the capsule transport security and (ii) high-capacity capsule transmission can be obtained. The important function is the capsule switching control which is also discussed. A brief review of theoretical background of multiwavelength soliton is also given.

Theoretical background

In Figure 1, a common semiconductor or tunable laser in any center wavelength can be used as a light source and launched into the propose system. A schematic diagram of a Gaussian soliton generation system using PANDA ring circuit pumping, which there is a linear add-drop filter included in the system. The fraction of light passing across the coupling area is written as whereas the fraction of light passing through the coupling area is written as , where the index i is denoted as the outer coupling area (1 and 2) and the inner right and left coupling area (R and L). γ_i is the intensity insertion loss coefficient, and κ_i is the coupling factor. The through-port transfer function can be calculated using SFG method, which is expressed as (Bahadoran et al. 2013)

(1)

where denotes a multiplication of a roundtrip parameter () and the Z-transform parameter () of main ring, right ring and left ring, respectively. Here α is the intensity attenuation coefficient and L is the optical path length of each ring resonator. k is the vacuum wave number, n_eff is the waveguide effective refractive index, and b is the main ring resonant number (N), right ring (NR) and left ring (NL). For add-drop ring resonator, the radius of the ring is 10 μm, where the through-port transfer function is expressed by

(1)

where

The PANDA ring resonator can be fabricated by the III–V semiconductor waveguide, where the group refractive index n_g is 3.46 (Prabhu et al. 2010). The PANDA main ring radius is 20 μm, where two side ring radii are 5 μm, the effective area (A_eff) of the ring is 0.30 μm². The intensity insertion loss coefficients (γ) is set as 0.1, and the attenuation coefficients (α) is supposed to be 0.2 dBmm^{− 1} for all couplers. The resonant number is N = 9 and NR = NL = 6 for the main ring and the both side rings. The outer coupling factors (κ₁ and κ₂) are symmetrically fixed by 0.65, where the inner coupling factors (κ_R and κ_L) are equally set by 0.15. In Figure 1, the extension link with add-drop ring resonator is constructed from Silicon-on-insulator waveguide, where the group refractive index ng is 4.306 (Prabhu et al. 2010). The insertion loss coefficients, the attenuation coefficients, and the outer coupling factors are supposed to be the same values of the PANDA ring resonator. The transmission losses are 0.01–0.1 dBm^{− 1} depending on the wavelength (Zou et al. 1997). In this paper, the transmission losses of all solitons are considered to be 0.05dBm^{− 1}, the nonlinear refractive index (n₂) is 1.3 × 10^{− 17} cm²/W.

Results

In simulation, a common laser (i.e., laser pointer) is exploited as a laser source. The optical power is the same as a common laser peak power, which is normally at 3.0(or higher) mW, however, the normalized output power is required for comparison. The simulation results are obtained using the practical parameters, the MATLAB program is used to obtain the results. In principle, the common laser pulse can be changed to be a soliton pulse by the resonant pumping power via the two side rings, which is occurred and seen via the add-drop filter output via the through and drop ports. In this simulation, the center ring radius of 20 μm is supposed to be the input main ring circuit, where the two nonlinear side ring radii are 5 μm.

The center ring and nonlinear materials are SiO₂ and InGaAsP/InP respectively. The waveguide attenuation coefficients (α) is 0.2 dBmm^{− 1} (Prabhu et al. 2010). The output transfer function is obtained using the signal flow graph method (Bahadoran et al. 2013). The resonant number of the main ring and side rings (N: NR: NL) are chosen as 9:6:6. The outer coupling factors κ₁ and κ₂ of PANDA ring resonator are fixed as 0.65 and the inner coupling factors (κ_R and κ_L) are set as 0.35. A round-trip time of the PANDA circuit at the resonant is 4.35 ps.

In Figure 2, the results of multicolor solitons propagation in the system with wavelength center at 0.9, 1.30, and 1.45 μm are obtained, where PANDA through and drop port signals are shown in red and in blue, respectively, in which the capsules can be formed by the bright and dark soliton pairs(orthogonal solitons). In Figure 3, the results of multicolor solitons propagation in the system with wavelength center at 0.55, 1.65, and 1.45 μm are obtained, where (a) the PANDA ring circuit signals, (b) the add-drop filter signals, the through and drop port signals are shown in red and in blue, respectively, in which the add-drop signals are decreased comparing to the PANDA signals, while the soliton behaviors of latter signals remain. In application, the longer propagation distance can be configured using the extended link, which is presented by more installing add-drop filter devices, where in this case study the obtained power (arbitrary unit) from through port of PANDA ring, first add-drop, second add-drop and third add-drop are 82.19%, 76.81%, 59.00%, and 45.32% comparing with the input port of the PANDA ring circuit, respectively.

Figure 2. Results of color soliton propagation in the system with wavelength center at 0.9, 1.30, and 1.45 μm, where PANDA through-port signals are Red: through–port signals, Blue: drop port signals.

Figure 3. Results of color soliton propagation in the system with wavelength center at 0.9, 1.30, and 1.45 μm, where (a) PANDA signals are (b) Add-drop signals, where Red: through port signals, Blue: drop port signals.

Results of the through-port outputs can be used for longer propagation distance in the transmission system, in which the required devices are add-drop filters. The soliton outputs are also obtained as shown in Figures 4 and 5, the through-port results from the longer distances are obtained using the Add and Drop ports #2 and #3, which confirmed that the soliton behaviors remain, where the optical power has slightly changed from 0.8 to 0.5 at the center wavelengths. The simulation results of multiwavelength solitons are obtained, where the obtained soliton power with propagation distance is as shown in Figure 4, in which the concept of soliton is occurred because the soliton power attenuation is slightly seen along the propagation distance, which the soliton power can be recovered by two soliton behaviors known as self-phase and cross-phase modulations. The soliton outputs with different wavelengths are obtained and shown in Figure 5, where, in general, the multicolor solitons can be easily obtained using the same method.

Figure 4. Results of color soliton propagation in the system with wavelength center at 0.58 μm, where the normalized power has slightly changed from 0.8 to 0.5 with distance of 16.6 m.

Figure 5. Color soliton output signals, the center wavelength is 0.58 micron, in which the multicolor solitons (different wavelengths) is obtained by using the proposed system.

Molecular capsule transporters

In applications, multicolor solitons have shown the promising applications, especially, for long-distance propagation within the light media, where (i) they offer a truly unique laboratory for soliton phenomena, where multicolor solitons are existed in the spatial and the temporal domains. They existed in guided and in bulk media, where they are existed in any physical dimensions, and thus they have the potential to form three-dimensional light bullets.

They existed in continuous and in discrete physical settings, and they are the realization of a universal phenomenon in nature, namely, the nonlinear parametric mixing of waves, where (ii) multicolor solitons offer clean, robust, stabilized, particle-like pulses. These beams could play key roles in future passive or active, single pass or cavity, multifrequency photonic devices for which the price of operation at high peak power is offset by the unique features of the soliton light spots. In Figure 6, graphics of optical capsules, where optical capsule model with trapped molecules with center wavelength at 1.45–1.5 μm, where F_grad: Gradient force, F_scatt: Scattering force, where F_scatt is smaller than F_grad for transportation use, (b) finite difference time domain (FDTD) Opti-wave results.

Figure 6. Graphics of optical capsules, where (a) with trapped molecules, (b) the 3D capsules obtained by Opti-wave, F_grad: Gradient force, F_scatt: Scattering force, WGM: whispering gallery mode.

In Figure 7, shows the drug delivery networks for long-distance drug delivery targeting security using optical capsules, where (a) tree and (b) ring and star networks. The light source can be a soliton or common laser source, which is allowed to generate the soliton output pulses. The network stability of the system in Figure 7 has already been calculated by the authors in references (Mitatha et al. 2011, Moongfangklang et al. 2011). The trapped substances can be probed by the generated capsules and transported to the desired targets. The trapped molecules in the capsules can be retrieved by using the molecular filtering device via the end users, which is operated by the capsule switching “ON-OFF” control, where finally the required trapped molecules or substances can be obtained. Using the design system, such devices can be constructed and implemented using the thin film technology and embedded within the body for any required diagnosis and medical treatments.

Figure 7. Drug delivery networks for long-distance drug delivery targeting security using optical capsules, where (a) tree network, (b) ring and star networks.

Conclusion

We have demonstrated that multicolor solitons can be simply generated and used for drug delivery in the small-scale optical devices and systems, where the trapped molecules/substances can be securely transported into the optical networks, while the high capacity is the another advantage. In a case study result, we have also shown that the dominant soliton behaviors such as long-lasting propagation time and pulse stability can offer the good potential of medical applications, which can be constructed and implemented within the small-scale optical systems, where in this case study, we found that the capsule propagation length of 16.6 m at the center wavelength of 0.58 μm is confirmed, which can be useful for new era of medical applications, in which the interaction between light and living cells (organs) can be long-lasting operation within a handset (portable) devices, where the medical diagnosis, therapy, and other investigations can be realized in the near future.

Acknowledgment

The authors would like to give the acknowledgement to King Mongkut's Institute of Technology Ladkrabang (KMITL), Bangkok 10520, Thailand for the laboratory facilities.

Declaration of interest

The authors report no declarations of interest. The authors alone are responsible for the content and writing of the paper.